[SCSI] lpfc: fix problems with -Werror

Commit d38bd3aef ("Add -Werror compilation flag") is causing build breakage
with random gcc incarnations.  These look like gcc problems, but we shouldn't
break the build because of a bad gcc.  Fix this by adding a make flag

WARNINGS_BECOME_ERRORS=1

which is the same as aic7xxx uses so ordinarily the build doesn't use -Werror
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Cc: Alex Iannicelli <alex.iannicelli@emulex.com>
Cc: James Smart <james.smart@emulex.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

drivers/scsi/lpfc/Makefile

@@ -22,7 +22,9 @@
 ccflags-$(GCOV) := -fprofile-arcs -ftest-coverage
 ccflags-$(GCOV) += -O0
 
+ifdef WARNINGS_BECOME_ERRORS
 ccflags-y += -Werror
+endif
 
 obj-$(CONFIG_SCSI_LPFC) := lpfc.o