ARM: imx: select SRC for i.MX7

The i.MX7 Kconfig option had a couple of missing select lines that
I fixed already, but I missed HAVE_IMX_SRC:

arch/arm/mach-imx/built-in.o: In function `imx7d_init_irq':
platform-spi_imx.c:(.init.text+0x25a8): undefined reference to `imx_src_init'

This adds that one as well.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 0be5da9d ("ARM: imx: imx7d requires anatop")
Signed-off-by: Shawn Guo <shawnguo@kernel.org>