intel: Don't check for context pointer to be NULL during extension init

intel: Don't check for context pointer to be NULL during extension init

Thanks to Chia-I Wu's changes to the extension function
infrastructure, we no longer have to tell the loader which extensions
the driver might enable.  This means that intelInitExtensions will
never be called with a NULL context pointer.  Remove all the NULL checks.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Eric Anholt <eric@anholt.net>