signal/sparc: si_trapno is only used with SIGILL ILL_ILLTRP

signal/sparc: si_trapno is only used with SIGILL ILL_ILLTRP

While reviewing the signal handlers on sparc it became clear that
si_trapno is only set to a non-zero value when sending SIGILL with
si_code ILL_ILLTRP.

Add force_sig_fault_trapno and send SIGILL ILL_ILLTRP with it.

Remove the define of __ARCH_SI_TRAPNO and remove the always zero
si_trapno parameter from send_sig_fault and force_sig_fault.

v1: https://lkml.kernel.org/r/m1eeers7q7.fsf_-_@fess.ebiederm.org
v2: https://lkml.kernel.org/r/20210505141101.11519-7-ebiederm@xmission.com
Link: https://lkml.kernel.org/r/87mtqnxx89.fsf_-_@disp2133
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>