video: offb: annotate implicit fall throughs

There is a plan to build the kernel with -Wimplicit-fallthrough and
these places in the code produced warnings (W=1). Fix them up.

This commit remove the following warnings:

drivers/video/fbdev/offb.c:211:5: warning: this statement may fall through [-Wimplicit-fallthrough=]
drivers/video/fbdev/offb.c:142:3: warning: this statement may fall through [-Wimplicit-fallthrough=]

Signed-off-by: Mathieu Malaterre <[e-mail]>
Acked-by: Gustavo A. R. Silva <[e-mail]>
Signed-off-by: Bartlomiej Zolnierkiewicz <[e-mail]>

drivers/video/fbdev/offb.c

···
 		/* Clear PALETTE_ACCESS_CNTL in DAC_CNTL */
 		out_le32(par->cmap_adr + 0x58,
 			 in_le32(par->cmap_adr + 0x58) & ~0x20);
+		/* fall through */
 	case cmap_r128:
 		/* Set palette index & data */
 		out_8(par->cmap_adr + 0xb0, regno);
···
 				/* Clear PALETTE_ACCESS_CNTL in DAC_CNTL */
 				out_le32(par->cmap_adr + 0x58,
 					 in_le32(par->cmap_adr + 0x58) & ~0x20);
+				/* fall through */
 			case cmap_r128:
 				/* Set palette index & data */
 				out_8(par->cmap_adr + 0xb0, i);