ARM: OMAP2+: Fix warnings for GPMC interrupt

ARM: OMAP2+: Fix warnings for GPMC interrupt

Commit db97eb7dfe13f6c04f0a0e77c32e2691f563ab8b
(omap: gpmc: enable irq mode in gpmc) enabled interrupts for
GPMC (General Purpose Memory Controller). However, looks like
this patch only works on omap3. Fix the issues to avoid warnings
on omap4 during the boot.

GPMC: number of chip select is 8, CS0 to CS7. One less IRQ
allocated throws below warning at boot:

[    0.429290] Trying to install type control for IRQ409
[    0.429290] Trying to set irq flags for IRQ409

Resolve following warning messages in boot when irq chip is not set:

[    0.429229] Trying to install interrupt handler for IRQ402
[    0.429229] Trying to install interrupt handler for IRQ403
[    0.429229] Trying to install interrupt handler for IRQ404
[    0.429260] Trying to install interrupt handler for IRQ405
[    0.429260] Trying to install interrupt handler for IRQ406
[    0.429260] Trying to install interrupt handler for IRQ407
[    0.429290] Trying to install interrupt handler for IRQ408

Resolve following warning in OMAP4:
[    0.429290] gpmc: irq-20 could not claim: err -22

Signed-off-by: Balaji T K <balajitk@ti.com>
[tony@atomide.com: combined patches into one, updated comments]
Signed-off-by: Tony Lindgren <tony@atomide.com>