sparc: fix a link error

Before this commit, arch/sparc/lib/Makefile used
both COBJS and COBJS-y.
And it missed to add COBJS-y into OBJS.
This means bootm.o was never compiled even if
CONFIG_CMD_BOOTM=y

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Daniel Hellstrom <daniel@gaisler.com>

arch/sparc/lib/Makefile

@@ -14,6 +14,8 @@ SOBJS	=
 COBJS	= board.o cache.o interrupts.o time.o
 COBJS-$(CONFIG_CMD_BOOTM) += bootm.o
 
+COBJS := $(COBJS) $(COBJS-y)
+
 SRCS	:= $(SOBJS:.o=.S) $(COBJS:.o=.c)
 OBJS	:= $(addprefix $(obj),$(SOBJS) $(COBJS))