staging:rtl8192u: Rename EEPROM_TxPwIndex_OFDM_24G - Style

Rename the constant EEPROM_TxPwIndex_OFDM_24G to
EEPROM_TX_PW_INDEX_OFDM_24G, this change clears the checkpatch
issue with CamelCase naming.

This change is a coding style change which should have no impact
on runtime code execution.

Signed-off-by: John Whitmore <johnfwhitmore@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>