staging: sm750fb: change definition of VGA_CONFIGURATION multi-bit field

Use more straight-forward definitions for multi-bit field of
VGA_CONFIGURATION register.
Signed-off-by: Mike Rapoport <mike.rapoport@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/sm750fb/ddk750_reg.h

@@ -547,7 +547,7 @@
 #define MXCLK_PLL_CTRL                                0x000070
 
 #define VGA_CONFIGURATION                             0x000088
-#define VGA_CONFIGURATION_USER_DEFINE                 5:4
+#define VGA_CONFIGURATION_USER_DEFINE_MASK            (0x3 << 4)
 #define VGA_CONFIGURATION_PLL                         BIT(2)
 #define VGA_CONFIGURATION_MODE                        BIT(1)