convert gprof flags to style of rest of Makefile

Signed-off-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Message-Id: 
diff --git a/Makefile.target b/Makefile.target
index 036c88f..08d9e96 100644
--- a/Makefile.target
+++ b/Makefile.target
@@ -285,10 +285,7 @@
 obj-m68k-y = an5206.o mcf5206.o mcf_uart.o mcf_intc.o mcf5208.o mcf_fec.o
 obj-m68k-y += m68k-semi.o dummy_m68k.o
 
-# profiling code
-ifdef TARGET_GPROF
-main.o vl.o: QEMU_CFLAGS+=-p
-endif
+main.o vl.o: QEMU_CFLAGS+=$(GPROF_CFLAGS)
 
 vl.o: QEMU_CFLAGS+=$(SDL_CFLAGS)