This is broken on big endian systems since:

943b271 cfi_flash: support of u32 cmd

I looked over it and I *think* that the function was correct
for both big and little endian systems before this patch.
To support u32 cmd we only have to change the data type of
the command from u8 to u32.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Teresa Gámez <t.gamez@phytec.de>