Fix memory commands for 64-bit platforms

For aarch64, unsigned long is 64-bit data. Memory commands should be fixed
with u32 for 32-bit address access. To be clear, ushort is replace with
u16, u_char is replaced with u8.

Signed-off-by: York Sun <yorksun@freescale.com>
Acked-by: Wolfgang Denk <wd@denx.de>