hvf: arm: Add permission check in GIC sysreg handlers

hvf: arm: Add permission check in GIC sysreg handlers

Quoting Peter Maydell:

" hvf_sysreg_read_cp() and hvf_sysreg_write_cp() do not check the .access
  field of the ARMCPRegInfo to ensure that they forbid writes to registers
  that are marked with a .access field that says they're read-only (and
  ditto reads to write-only registers). "

Before we add more registers in GIC sysreg handlers, let's get it correct
by adding the .access checks to hvf_sysreg_read_cp() and
hvf_sysreg_write_cp(). With that, a sysreg access with invalid permission
will result in an UNDEFINED exception.

Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Zenghui Yu <zenghui.yu@linux.dev>
Message-id: 20250714160139.10404-2-zenghui.yu@linux.dev
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>