arm64: disable trapping of POR_EL0 to EL2

arm64: disable trapping of POR_EL0 to EL2

Allow EL0 or EL1 to access POR_EL0 without being trapped to EL2.

Signed-off-by: Joey Gouly <joey.gouly@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Link: https://lore.kernel.org/r/20240822151113.1479789-5-joey.gouly@arm.com
[will: Rename Lset_poe_fgt to Lskip_pie_fgt to ease merge with for-next/misc]
Signed-off-by: Will Deacon <will@kernel.org>