runtime: use entersyscall in syscall_syscallX on Darwin
runtime: use entersyscall in syscall_syscallX on Darwin

CL 197938 changed syscall* functions to call entersyscall, instead
of entersyscallblock. It missed syscall_syscallX, probably because
it was in sys_darwin_64.go, not sys_darwin.go like others. Change
that one as well.

Found during the review of CL 270380 (thanks Joel).

Change-Id: I0884fc766703f555a3895be332dccfa7d2431374
Reviewed-on: https://go-review.googlesource.com/c/go/+/286435
Trust: Cherry Zhang <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>
Run-TryBot: Cherry Zhang <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>
TryBot-Result: Go Bot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

golang/go,nawawi/go,golang/go,nawawi/go,cloudflare/go,CAFxX/go,golang/go,CAFxX/go,golang/go,nawawi/go,golang/go,cloudflare/go,CAFxX/go,CAFxX/go,golang/go,cloudflare/go,nawawi/go,golang/go,CAFxX/go,CAFxX/go,CAFxX/go,cloudflare/go,cloudflare/go,nawawi/go,cloudflare/go,golang/go,cloudflare/go,CAFxX/go,nawawi/go,nawawi/go,nawawi/go,cloudflare/go