drivers: intc_gicv3_its: fix incorrect RDbase when PE number is used

For RDbase used by its command, When GITS_TYPER.PTA = 1, physicall address
is used, the RDbase field consist of bits[51:16] of the address, so need
to left shift the address by 16 bits. But when GITS_TYPER.PTA = 0, PE
number is used, no need to shit anymore.

Signed-off-by: Jiafei Pan <Jiafei.Pan@nxp.com>