bsd-user:Add ARM AArch64 support and capabilities

bsd-user:Add ARM AArch64 support and capabilities

Added function to access rval2 by accessing the x1 register.
Defined ARM AArch64 ELF parameters including mmap and dynamic load addresses.
Introduced extensive hardware capability definitions and macros for retrieving hardware capability (hwcap) flags.
Implemented function to retrieve ARM AArch64 hardware capabilities using the `GET_FEATURE_ID` macro.
Added function to retrieve extended ARM AArch64 hardware capability flags.

Signed-off-by: Stacey Son <sson@FreeBSD.org>
Signed-off-by: Ajeet Singh <itachis@FreeBSD.org>
Signed-off-by: Warner Losh <imp@bsdimp.com>
Co-authored-by: Kyle Evans <kevans@FreeBSD.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20240707191128.10509-4-itachis@FreeBSD.org>
Signed-off-by: Warner Losh <imp@bsdimp.com>