internal/cpu: remove parentheses from arm64 feature constants
internal/cpu: remove parentheses from arm64 feature constants

The parentheses are not required for the definitions and it brings
the declaration style in line with other architectures feature bits
defined in internal/cpu.

Change-Id: I86cc3812c1488216779e0d1f0e7481687502e592
Reviewed-on: https://go-review.googlesource.com/126775
Run-TryBot: Martin Möhrmann <9c82b83f348009b39856043bb9ed3ef41e171aeb@google.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Cherry Zhang <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>

josharian/go,golang/go,cloudflare/go,golang/go,nawawi/go,josharian/go,akutz/go,josharian/go,CAFxX/go,cloudflare/go,golang/go,CAFxX/go,akutz/go,josharian/go,akutz/go,josharian/go,golang/go,golang/go,josharian/go,cloudflare/go,akutz/go,akutz/go,akutz/go,golang/go,nawawi/go,nawawi/go,nawawi/go,cloudflare/go,golang/go,CAFxX/go,cloudflare/go,CAFxX/go,akutz/go,CAFxX/go,golang/go,nawawi/go,josharian/go,akutz/go,josharian/go,nawawi/go,cloudflare/go,cloudflare/go,nawawi/go,CAFxX/go,nawawi/go,CAFxX/go,cloudflare/go,CAFxX/go