MIPS: Fix IRQ tracing when call handle_fpe() and handle_msa_fpe()

[ Upstream commit 31e1b3efa802f97a17628dde280006c4cee4ce5e ]

Register "a1" is unsaved in this function,
 when CONFIG_TRACE_IRQFLAGS is enabled,
 the TRACE_IRQS_OFF macro will call trace_hardirqs_off(),
 and this may change register "a1".
 The changed register "a1" as argument will be send
 to do_fpe() and do_msa_fpe().

Signed-off-by: YuanJunQing <yuanjunqing66@163.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>