arm64: zynqmp: Fix logic in CG/EG/EV detection

arm64: zynqmp: Fix logic in CG/EG/EV detection

The VCU disable bit(8) in IP disable register of efuse
is valid only if PL powered up and hence PL powerup status
has to be considered while determining the CG part also.
This patch considers the PL powerup status and ignores the VCU
disable bit if PL not powered up.
This fixes the issue of "unknown" id for CG parts if PL not powered up
and VCU bit(8) is not set.

Signed-off-by: Siva Durga Prasad Paladugu <siva.durga.paladugu@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>