sh: Don't enable interrupts in the page fault path

There's already code in do_page_fault() to conditionally enable
interrupts, so we don't need to unconditonally enable them before
calling it. This fixes a lockdep warning where we called
trace_hardirqs_off() but with irqs still enabled.

Signed-off-by: Matt Fleming <matt@console-pimps.org>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>