staging: wilc1000: remove typedef from CURRENT_TX_RATE_T

This patch remove typedef from the enum CURRENT_TX_RATE_T.
And rename it to CURRENT_TXRATE.

Signed-off-by: Leo Kim <leo.kim@atmel.com>
Signed-off-by: Tony Cho <tony.cho@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>