i965: Use allow_higher_compat_version option during screen initialization

i965: Use allow_higher_compat_version option during screen initialization

Currently, `allow_higher_compat_version` is only used during context
creation.  Doing that means an application that doesn't request a
specific version can be given a version higher than 3.0.

However, an application still cannot request a higher version via
glXCreateContextAttribsARB.  The GLX and DRI layers will only see that
version 3.0 is supported, so context creation will fail before the drive
is called.  For this to work, max_gl_compat_version must be set to a
higher version.

This enables running many piglit tests on i965 with
allow_higher_compat_version.

v2: Fix a typo in a comment.  Noticed by Tim.  Fix a typo in the commit
message.  Noticed by the spell checker. :)

v3: Don't parse driconf again.  Suggested by Tim.

Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7387>