arm64: entry: Refactor the entry and exit for exceptions from EL1

arm64: entry: Refactor the entry and exit for exceptions from EL1

The generic entry code uses irqentry_state_t to track lockdep and RCU
state across exception entry and return. For historical reasons, arm64
embeds similar fields within its pt_regs structure.

In preparation for moving arm64 over to the generic entry code, pull
these fields out of arm64's pt_regs, and use a separate structure,
matching the style of the generic entry code.

No functional changes.

Acked-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Ada Couprie Diaz <ada.coupriediaz@arm.com>
Suggested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>