staging: sm750fb: Replace uint32_t with u32

Replace uint32_t with u32 consistent with Linux kernel coding
practice.
Problem found using checkpatch.pl

Signed-off-by: Amitoj Kaur Chawla <amitoj1606@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>