staging: fbtft: Remove the use of CamelCase

Rename the macro defining constant ROWxCOL into ROW_X_COL to remove
checkpatch check concerning use of CamelCase and to achieve better
readability.

CHECK: Avoid CamelCase: <ROWxCOL>

Signed-off-by: Eva Rachel Retuya <eraretuya@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>