m32r: consistently use "suffix-$(...)"

Commit a556bec9 ("m32r: fix arch/m32r/boot/compressed/Makefile")
changed "$(suffix_y)" to "$(suffix-y)", but didn't update any location
where "suffix_y" is set, causing:

  make[5]: *** No rule to make target `arch/m32r/boot/compressed/vmlinux.bin.', needed by `arch/m32r/boot/compressed/piggy.o'.  Stop.
  make[4]: *** [arch/m32r/boot/compressed/vmlinux] Error 2
  make[3]: *** [zImage] Error 2

Correct the other locations to fix this.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Hirokazu Takata <takata@linux-m32r.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>