fix(gic600): fix gic600 maximum SPI ID

According to GIC-600 TRM, it supports up to 960 SPIs. With the
starting SPI_ID of 32, the maximum SPI_ID should be 991. This patch
fixes the value of GIC600_SPI_ID_MAX which is currently configured
to be 960.

Signed-off-by: sahil <sahil@arm.com>
Change-Id: I441f9a607d160db8533f2a03e02afd1a9bab991e
2 files changed