staging: sm750fb: remove function pointer proc_setBLANK

Call a function based on sm750_dev->revid
instead of using this indirection

Signed-off-by: Kisub Choe <kisub.choe.0x1@gmail.com>
Link: https://lore.kernel.org/r/aFWSSAcboBVi4ROh@zinc


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>