video/logo: simplify cmd_logo

Shorten the code. It still works in the same way.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

drivers/video/logo/Makefile

@@ -22,20 +22,15 @@ pnmtologo := scripts/pnmtologo
 
 # Create commands like "pnmtologo -t mono -n logo_mac_mono -o ..."
 quiet_cmd_logo = LOGO    $@
-	cmd_logo = $(pnmtologo) \
-			-t $(patsubst $*_%,%,$(notdir $(basename $<))) \
-			-n $(notdir $(basename $<)) -o $@ $<
+      cmd_logo = $(pnmtologo) -t $(lastword $(subst _, ,$*)) -n $* -o $@ $<
 
-$(obj)/%_mono.c: $(src)/%_mono.pbm $(pnmtologo) FORCE
+$(obj)/%.c: $(src)/%.pbm $(pnmtologo) FORCE
 	$(call if_changed,logo)
 
-$(obj)/%_vga16.c: $(src)/%_vga16.ppm $(pnmtologo) FORCE
+$(obj)/%.c: $(src)/%.ppm $(pnmtologo) FORCE
 	$(call if_changed,logo)
 
-$(obj)/%_clut224.c: $(src)/%_clut224.ppm $(pnmtologo) FORCE
-	$(call if_changed,logo)
-
-$(obj)/%_gray256.c: $(src)/%_gray256.pgm $(pnmtologo) FORCE
+$(obj)/%.c: $(src)/%.pgm $(pnmtologo) FORCE
 	$(call if_changed,logo)
 
 # generated C files