Revert "ARM i.MX25: Fix PWM per clock lookups"

This reverts commit 92063cee, it
was applied prematurely, causing this build error for
imx_v4_v5_defconfig:

arch/arm/mach-imx/clk-imx25.c: In function 'mx25_clocks_init':
arch/arm/mach-imx/clk-imx25.c:206:26: error: 'pwm_ipg_per' undeclared (first use in this function)
arch/arm/mach-imx/clk-imx25.c:206:26: note: each undeclared identifier is reported only once for each function it appears in

Sascha Hauer explains:
> There are several gates missing in clk-imx25.c. I have a patch which
> adds support for them and I seem to have missed that the above depends
> on it.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>