Staging: sm750fb: Change *array into *const array

Resolve checkpatch warning for static const char * array by using const
pointers.

Checkpatch Warning in sm750.c:
static const char * array should probably be static const char * const

Signed-off-by: Kelsey Skunberg <skunberg.kelsey@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>