OMAP2/3 clock: don't tinker with hardirqs when they are supposed to be disabled

Clock rate change code executes inside a spinlock with hardirqs
disabled.  The only code that should be messing around with the
hardirq state should be the plat-omap/clock.c code.  In the
omap2_reprogram_dpllcore() case, this probably just wastes cycles, but
in the omap3_core_dpll_m2_set_rate() case, this is a nasty bug.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>