FRV: Don't turn on TIF_SYSCALL_TRACE unconditionally in syscall prologue

Don't turn on TIF_SYSCALL_TRACE unconditionally in syscall prologue in FRV's
entry.S.  This was originally for debugging stuff and should have been removed
a long time ago.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>