ARM: OMAP4+: PRM: fix omap4 version of prm_save_and_clear_irqen

This was incorrectly reading the irq status registers during the save
and clear, instead of the irq enable. This worked because there is only
one user for the prcm interrupts currently, namely the io-chain. Whenever
the function was called, an io-chain interrupt was both pending and
enabled.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Tony Lindgren <tony@atomide.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>