ARM: OMAP1: Amstrad Delta: Fix wrong IRQ base in FIQ handler

Commit 384ebe1c, "gpio/omap: Add DT
support to GPIO driver", introduced dynamic IRQ numbering of OMAP GPIO
interrupts, breaking all IH_GPIO_BASE based IRQ number calculations.
This issue was corrected in the OMAP GPIO driver and the related header
file with commit 25db711d, "gpio/omap:
Fix IRQ handling for SPARSE_IRQ".

However, the Amstrad Delta FIQ handler, which replaces the gpio-omap
driver in serving GPIO interrupts on this board, still uses that
outdated method. Fix it.

Signed-off-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
Signed-off-by: Tony Lindgren <tony@atomide.com>