Fix assertion in GIC ITS helper
Fix assertion in GIC ITS helper

This patch fixes an assertion check in the GICv3 ITS helper function.

Change-Id: I75f50d7bf6d87c12c6e24a07c9a9889e5facf4a5
Signed-off-by: Soby Mathew <4d7af7c5c404e07961f9e1e79d6f17409c1d7db7@arm.com>

lsigithub/arm-trusted-firmware_public,achingupta/arm-trusted-firmware,lsigithub/arm-trusted-firmware_public,achingupta/arm-trusted-firmware