SH: define syscall_get_arch() for superh

This patch defines syscall_get_arch() for the superh platform.  It does
so in both syscall_32.h and syscall_64.h.  I'm not certain if the
implementation in syscall_64.h couldn't just be used in syscall.h as I
can't really track the setting of CONFIG_64BIT...

This way is safe, but we might be able to combine these if a superh
person were able to review...

[v2]
	fixed indentation stoopidity (Sergei Shtylyov)
	use AUDIT_ARCH_SH instead of EM_SH

Based-on-patch-by: Richard Briggs <rgb@redhat.com>
Signed-off-by: Eric Paris <eparis@redhat.com>
Cc: linux-sh@vger.kernel.org