riscv/mm/fault: Simplify fault error handling

riscv/mm/fault: Simplify fault error handling

Move fault error handling after retry logic. This simplifies the code
flow and makes it easier to move fault error handling to its own
function.

Signed-off-by: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>