selftest/fpu: avoid clang warning

With extra warnings enabled, clang complains about the redundant
-mhard-float argument:

  clang: error: argument unused during compilation: '-mhard-float' [-Werror,-Wunused-command-line-argument]

Move this into the gcc-only part of the Makefile.

Link: https://lkml.kernel.org/r/20201203223652.1320700-1-arnd@kernel.org
Fixes: 4185b3b ("selftests/fpu: Add an FPU selftest")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Nathan Chancellor <natechancellor@gmail.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Petteri Aimonen <jpa@git.mail.kapsi.fi>
Cc: Borislav Petkov <bp@suse.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: arndb

lib/Makefile

@@ -107,7 +107,7 @@ obj-$(CONFIG_TEST_FREE_PAGES) += test_free_pages.o
 # off the generation of FPU/SSE* instructions for kernel proper but FPU_FLAGS
 # get appended last to CFLAGS and thus override those previous compiler options.
 #
-FPU_CFLAGS := -mhard-float -msse -msse2
+FPU_CFLAGS := -msse -msse2
 ifdef CONFIG_CC_IS_GCC
 # Stack alignment mismatch, proceed with caution.
 # GCC < 7.1 cannot compile code using `double` and -mpreferred-stack-boundary=3
@@ -120,6 +120,7 @@ ifdef CONFIG_CC_IS_GCC
 #  -mpreferred-stack-boundary=3 is not between 4 and 12
 #
 # can be triggered. Otherwise gcc doesn't complain.
+FPU_CFLAGS += -mhard-float
 FPU_CFLAGS += $(call cc-option,-msse -mpreferred-stack-boundary=3,-mpreferred-stack-boundary=4)
 endif