video/logo: remove orphan .pgm Makefile rule

The kernel has no actual grey-scale logos. And looking at the git
history, it seems that there never was one (or maybe there was in the
pre-git history? I did not check that far…)

Remove the Makefile rule for the .pgm grey scale images.

Signed-off-by: Vincent Mailhol <mailhol@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Helge Deller <deller@gmx.de>

Author: vincent-mailhol

drivers/video/logo/Makefile

@@ -30,8 +30,5 @@ $(obj)/%.c: $(src)/%.pbm $(obj)/pnmtologo FORCE
 $(obj)/%.c: $(src)/%.ppm $(obj)/pnmtologo FORCE
 	$(call if_changed,logo)
 
-$(obj)/%.c: $(src)/%.pgm $(obj)/pnmtologo FORCE
-	$(call if_changed,logo)
-
 # generated C files
-targets += *_mono.c *_vga16.c *_clut224.c *_gray256.c
+targets += *_mono.c *_vga16.c *_clut224.c