staging: sm750fb: rename `hw_sm750_setColReg`

Rename `hw_sm750_setColReg` to `hw_sm750_set_col_reg` to conform with
kernel style guidelines as reported by checkpatch.pl

CHECK: Avoid CamelCase: <hw_sm750_setColReg>

Signed-off-by: Eric Florin <ericflorin@google.com>
Link: https://lore.kernel.org/r/3d4bb87742eee4a6792bbdae893256f621ffffe6.1747619816.git.ericflorin@google.com


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