staging: rtl8192e: Remove bb tx gains from r8192_priv

r8192_priv structure had 2 big arrays with tx gain register values:
- cck_txbbgain_table
- cck_txbbgain_ch14_table
- txbbgain_table

This arrays were read-only - filled in driver init code and look
like firmware/chip-specific.

This patch removes them from r8192_priv and puts them in (global) variables.

tx_bb_gain is also flattened - register values are stored in array;
Amplification value can be calculated using dm_tx_bb_gain_idx_to_amplify().

Signed-off-by: Mateusz Kulikowski <mateusz.kulikowski@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>