imx: mmdc_size: Fix checkpatch warnings

The original imx_ddr_size() implementation had some
issues reported by checkpatch like this:

CHECK: Prefer kernel type 'u32' over 'uint32_t'
#127: FILE: arch/arm/mach-imx/mmdc_size.c:16:
+	uint32_t	ctl;

WARNING: Prefer 'unsigned int' to bare use of 'unsigned'
#151: FILE: arch/arm/mach-imx/mmdc_size.c:40:
+	unsigned ctl = readl(&mem->ctl);

Fix all of them.

Signed-off-by: Fabio Estevam <festevam@gmail.com>