GCC warns against bitfields not fitting the entire range of an enum
with a fixed underlying type of unsigned int, which gets promoted to
an error with -Werror and cannot be suppressed. However, GCC already
defaults to using unsigned int as the underlying type of an unscoped
enum without a fixed underlying type. So we can just omit it.

Bug chromium:697528

Change-Id: I8db8fef09e3397d4ec5ebe9f7c3c5e4ae9c0edff
Reviewed-on: https://swiftshader-review.googlesource.com/8928Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>