arch/openrisc: Fix issues with access_ok()

The commit 594cc251 ("make 'user_access_begin()' do 'access_ok()'")
exposed incorrect implementations of access_ok() macro in several
architectures.  This change fixes 2 issues found in OpenRISC.

OpenRISC was not properly using parenthesis for arguments and also using
arguments twice.  This patch fixes those 2 issues.

I test booted this patch with v5.0-rc1 on qemu and it's working fine.

Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Stafford Horne <shorne@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>