RISC-V: Avoid dereferening NULL regs in die()

RISC-V: Avoid dereferening NULL regs in die()

[ Upstream commit f2913d006fcdb61719635e093d1b5dd0dafecac7 ]

I don't think we can actually die() without a regs pointer, but the
compiler was warning about a NULL check after a dereference.  It seems
prudent to just avoid the possibly-NULL dereference, given that when
die()ing the system is already toast so who knows how we got there.

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20220920200037.6727-1-palmer@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Stable-dep-of: 130aee3fd998 ("riscv: Avoid enabling interrupts in die()")
Signed-off-by: Sasha Levin <sashal@kernel.org>