sh: also try passing -m4-nofpu for SH2A builds

When compiling a SH2A kernel (e.g.  se7206_defconfig or rsk7203_defconfig)
using sh4-linux-gcc, linking fails with:

  net/built-in.o: In function `__sk_run_filter':
  net/core/filter.c:566: undefined reference to `__fpscr_values'
  net/core/filter.c:269: undefined reference to `__fpscr_values'
  ...
  net/built-in.o:net/core/filter.c:580: more undefined references to `__fpscr_values' follow

This happens because sh4-linux-gcc doesn't support the "-m2a-nofpu",
which is thus filtered out by "$(call cc-option, ...)".

As compiling using sh4-linux-gcc is useful for compile coverage, also
try passing "-m4-nofpu" (which is presumably filtered out when using a
real sh2a-linux toolchain) to disable the generation of FPU instructions
and references to __fpscr_values[].

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Tony Breeds <tony@bakeyournoodle.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Daniel Borkmann <dborkman@redhat.com>
Cc: Magnus Damm <magnus.damm@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>