s390/sysinfo: allow compiler warnings again

Allow compiler warnings again for the sysinfo file. Compiler warnings
were disabled when the bogomips calculation with math-emu code was
introduced ("[S390] Calibrate delay and bogomips.").
Since that code is gone, we can enable warnings again.
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/Makefile

@@ -51,8 +51,6 @@ CFLAGS_dumpstack.o	+= -fno-optimize-sibling-calls
 #
 CFLAGS_ptrace.o		+= -DUTS_MACHINE='"$(UTS_MACHINE)"'
 
-CFLAGS_sysinfo.o	+= -w
-
 obj-y	:= traps.o time.o process.o base.o early.o setup.o idle.o vtime.o
 obj-y	+= processor.o sys_s390.o ptrace.o signal.o cpcmd.o ebcdic.o nmi.o
 obj-y	+= debug.o irq.o ipl.o dis.o diag.o vdso.o als.o