signal/sparc: Move EMT_TAGOVF into the generic siginfo.h

When moving all of the architectures specific si_codes into
siginfo.h, I apparently overlooked EMT_TAGOVF.  Move it now.

Remove the now redundant test in siginfo_layout for SIGEMT
as now NSIGEMT is always defined.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

include/uapi/asm-generic/siginfo.h

@@ -285,6 +285,12 @@ typedef struct siginfo {
 #define SYS_SECCOMP	1	/* seccomp triggered */
 #define NSIGSYS		1
 
+/*
+ * SIGEMT si_codes
+ */
+#define EMT_TAGOVF	1	/* tag overflow */
+#define NSIGEMT		1
+
 /*
  * sigevent definitions
  *