arm64/boot: Enable EL2 requirements for BRBE

Fine grained trap control for BRBE registers, and instructions access need
to be configured in HDFGRTR_EL2, HDFGWTR_EL2 and HFGITR_EL2 registers when
kernel enters at EL1 but EL2 is present. This changes __init_el2_fgt() as
required.

Similarly cycle and mis-prediction capture need to be enabled in BRBCR_EL1
and BRBCR_EL2 when the kernel enters either into EL1 or EL2. This adds new
__init_el2_brbe() to achieve this objective.

This also updates Documentation/arch/arm64/booting.rst with all the above
EL2 along with MDRC_EL3.SBRBE requirements.

First this replaces an existing hard encoding (1 << 62) with corresponding
applicable macro HDFGRTR_EL2_nPMSNEVFR_EL1_MASK.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Oliver Upton <oliver.upton@linux.dev>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
----
Changes in V17:

- New patch added in the series
- Separated out from the BRBE driver implementation patch
- Dropped the comment in __init_el2_brbe()
- Updated __init_el2_brbe() with BRBCR_EL2.MPRED requirements
- Updated __init_el2_brbe() with __check_hvhe() constructs
- Updated booting.rst regarding MPRED, MDCR_EL3 and fine grained control