net/wireless: Fix handling of supported-rates

Handling of supported-rates was duplicated by mistake
in two separate blocks and was done twice. In addition,
in the first block handling of supported-rates in
unsupported bands is missing.

Change-Id: Ic75dfb60fa2ae2be8010e1e1ef4400279c91809f
Signed-off-by: Hamad Kadmany <hkadmany@codeaurora.org>