After testing, it appears that the gxl (and axg) does not require the
special locking/reset loop which was initially added for it.

All the values present in the gxl table can locked with the simple lock
checking loop.

The change switches the gxl and axg gp0 back to the simple lock checking
loop and removes the code no longer required.
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>