Revert "rt2x00: rt2800lib: Update BBP register initialization for RT53xx"

This reverts commit eac40d96. It cause
random connection drops on RT5390 PCI adapters.

On Mediatek there is different driver version available for RT53xx chip
based on bus type (2.5.0.3 for PCI and 2.6.1.3 for USB). Hence possibly
we should set registers differently based on bus type. But is also
possible that new driver (i.e. 2.6.1.3) was not verified on RT53xx USB.

Until we figure out how to initialize registers properly for RT53xx just
revert commit eac40d96

 since it cause
regression.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>