GIC: Add APIs to enable and disable interrupt

API documentation updated.

Change-Id: Ice7511f8df5356851001d2f7dc2a46cfe318f9ba
Co-authored-by: Yousuf A <yousuf.sait@arm.com>
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
10 files changed