feat(versal): add support to reset SGI

Add "reset" parameter in pm_register_sgi() to reset
SGI number. This will be required if OS wants to reset
SGI number to default state. Caller can reset param to
1 to reset SGI in ATF.

Change-Id: If485ff275df884f74eb67671cac7fa953458afe9
Signed-off-by: Rajan Vaja <rajan.vaja@xilinx.com>
Signed-off-by: Tanmay Shah <tanmay.shah@xilinx.com>