m68k: mac: Remove unused rbv_set_video_bpp()

In examining rbv_set_video_bpp()'s improper usage of a non-explictly
signed char type, it turns out that the function is actually unused.
So remove it.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Link: https://lore.kernel.org/r/20221026130051.1577286-1-Jason@zx2c4.comSigned-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

arch/m68k/include/asm/mac_via.h

@@ -267,14 +267,6 @@ extern void via1_irq(struct irq_desc *desc);
 extern void via1_set_head(int);
 extern int via2_scsi_drq_pending(void);
 
-static inline int rbv_set_video_bpp(int bpp)
-{
-	char val = (bpp==1)?0:(bpp==2)?1:(bpp==4)?2:(bpp==8)?3:-1;
-	if (!rbv_present || val<0) return -1;
-	via2[rMonP] = (via2[rMonP] & ~RBV_DEPTH) | val;
-	return 0;
-}
-
 #endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_MAC_VIA_H_ */