spi/imx: Fix spi-imx when the hardware SPI chipselects are used

commit 22a85e4c (spi/imx: add device tree probe support) broke spi-imx usage
when the SPI chipselect is the one internal to the controller.

On a mx31pdk board the following error is seen:

Registering mxc_nand as whole device
------------[ cut here ]------------
WARNING: at drivers/gpio/gpiolib.c:101 gpio_ensure_requested+0x4c/0xf4()
autorequest GPIO-0
Modules linked in:
[<c0014410>] (unwind_backtrace+0x0/0xf4) from [<c0025754>] (warn_slowpath_common+0x4c/0x64)
[<c0025754>] (warn_slowpath_common+0x4c/0x64) from [<c0025800>] (warn_slowpath_fmt+0x30/0x40)
[<c0025800>] (warn_slowpath_fmt+0x30/0x40) from [<c0198688>] (gpio_ensure_requested+0x4c/0xf4)
[<c0198688>] (gpio_ensure_requested+0x4c/0xf4) from [<c01988c8>] (gpio_direction_output+0xa0/0x138)
[<c01988c8>] (gpio_direction_output+0xa0/0x138) from [<c01ed198>] (spi_imx_setup+0x38/0x4c)
[<c01ed198>] (spi_imx_setup+0x38/0x4c) from [<c01eb5d0>] (spi_setup+0x38/0x50)
[<c01eb5d0>] (spi_setup+0x38/0x50) from [<c01eb85c>] (spi_add_device+0x94/0x124)
[<c01eb85c>] (spi_add_device+0x94/0x124) from [<c01eb960>] (spi_new_device+0x74/0xac)
[<c01eb960>] (spi_new_device+0x74/0xac) from [<c01eb9b8>] (spi_match_master_to_boardinfo+0x20/0x40)
[<c01eb9b8>] (spi_match_master_to_boardinfo+0x20/0x40) from [<c01eba88>] (spi_register_master+0xb0/0x104)
[<c01eba88>] (spi_register_master+0xb0/0x104) from [<c01ec0b4>] (spi_bitbang_start+0x104/0x17c)
[<c01ec0b4>] (spi_bitbang_start+0x104/0x17c) from [<c02c2c4c>] (spi_imx_probe+0x2fc/0x404)
[<c02c2c4c>] (spi_imx_probe+0x2fc/0x404) from [<c01c2498>] (platform_drv_probe+0x18/0x1c)
[<c01c2498>] (platform_drv_probe+0x18/0x1c) from [<c01c1058>] (driver_probe_device+0x78/0x174)
[<c01c1058>] (driver_probe_device+0x78/0x174) from [<c01c11e0>] (__driver_attach+0x8c/0x90)
[<c01c11e0>] (__driver_attach+0x8c/0x90) from [<c01c0860>] (bus_for_each_dev+0x60/0x8c)
[<c01c0860>] (bus_for_each_dev+0x60/0x8c) from [<c01c0088>] (bus_add_driver+0xa0/0x288)
[<c01c0088>] (bus_add_driver+0xa0/0x288) from [<c01c179c>] (driver_register+0x78/0x18c)
[<c01c179c>] (driver_register+0x78/0x18c) from [<c0008490>] (do_one_initcall+0x34/0x178)
[<c0008490>] (do_one_initcall+0x34/0x178) from [<c03a5204>] (kernel_init+0x74/0x118)
[<c03a5204>] (kernel_init+0x74/0x118) from [<c000f65c>] (kernel_thread_exit+0x0/0x8)
---[ end trace 759f924b30fd5a44 ]---

Fix this issue by using the original chip select logic and make spi-imx to work again.

Tested on a mx31pdk that uses the hardware SPI chipselect pins and also
on a mx27pdk that uses GPIO as SPI chipselect.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>