staging: sm750fb: fix CamelCase variable naming

Replace CamelCase variable 'Bpp' with lowercase 'bpp' to fix
checkpatch warnings about improper variable naming convention.

Signed-off-by: Ignacio Pena <ignacio.pena87@gmail.com>
Link: https://lore.kernel.org/r/20250716181718.82227-1-ignacio.pena87@gmail.com


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