Under arm64 elf_hwcap is a 32 bit quantity, but it is stored in
a 64 bit auxiliary ELF field and glibc reads hwcap as 64 bit.

This patch widens elf_hwcap to be 64 bit.
Signed-off-by: NSteve Capper <steve.capper@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>