microblaze: Correct PVR access macros

A definition like:

called with PVR_IS_FULL(foo) will be preprocessed to:

(foo.foo[0] & PVR0_PVR_FULL_MASK)
     ^^^
So to fix this and ensure the preprocessor compiles calls correctly:

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Michal Simek <monstr@monstr.eu>