Let's use existing ISS encoding for an watchpoint exception i.e ESR_ELx_WNR
This represents an instruction's either writing to or reading from a memory
location during an watchpoint exception. While here this drops non-standard
macro AARCH64_ESR_ACCESS_MASK.

Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20240229083431.356578-1-anshuman.khandual@arm.comSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>