riscv/mm: Simplify retry logic in do_page_fault()

riscv/mm: Simplify retry logic in do_page_fault()

Let's combine the two retry logic if statements in do_page_fault() to
simplify the code.

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