perf trace: Decode architecture-specific signal numbers

perf trace: Decode architecture-specific signal numbers

SIGSTKFLT is not defined on alpha, mips or sparc.

SIGEMT and SIGSWI are defined on some architectures and should be
decoded here if so.

Signed-off-by: Ben Hutchings <[email protected]>
Fixes: 8bad5b0abfdb ('perf trace: Beautify signal number arg in several syscalls')
Cc: Ingo Molnar <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>