ARM: 8035/1: Disable preemption in crunch_task_enable()

This patch is in preparation for calling the crunch_task_enable()
function with interrupts enabled.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ryan Mallon <rmallon@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>