signal/sparc32: Remove unreachable do_exit in do_sparc_fault

The call to do_exit in do_sparc_fault immediately follows a call to
unhandled_fault.  The function unhandled_fault never returns.  This
means the call to do_exit can never be reached.

Cc: David Miller <davem@davemloft.net>
Cc: sparclinux@vger.kernel.org
Fixes: 2.3.41
Link: https://lkml.kernel.org/r/20211020174406.17889-4-ebiederm@xmission.com
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>