rtlwifi: rtl8192_common: Fix smatch errors and warnings in rtl8192c/dm_common.c

Smatch lists the following:
  CHECK   drivers/net/wireless/rtlwifi/rtl8192c/dm_common.c
drivers/net/wireless/rtlwifi/rtl8192c/dm_common.c:551 rtl92c_dm_pwdb_monitor() info: ignoring unreachable code.
drivers/net/wireless/rtlwifi/rtl8192c/dm_common.c:551 rtl92c_dm_pwdb_monitor() info: ignoring unreachable code.
drivers/net/wireless/rtlwifi/rtl8192c/dm_common.c:870 rtl92c_dm_txpower_tracking_callback_thermalmeter() error: buffer overflow 'txpwr_level' 2 <= 2
drivers/net/wireless/rtlwifi/rtl8192c/dm_common.c:870 rtl92c_dm_txpower_tracking_callback_thermalmeter() error: buffer overflow 'txpwr_level' 2 <= 2
drivers/net/wireless/rtlwifi/rtl8192c/dm_common.c:882 rtl92c_dm_txpower_tracking_callback_thermalmeter() error: buffer overflow 'txpwr_level' 2 <= 2
drivers/net/wireless/rtlwifi/rtl8192c/dm_common.c:883 rtl92c_dm_txpower_tracking_callback_thermalmeter() error: buffer overflow 'txpwr_level' 2 <= 2
drivers/net/wireless/rtlwifi/rtl8192c/dm_common.c:891 rtl92c_dm_txpower_tracking_callback_thermalmeter() error: buffer overflow 'txpwr_level' 2 <= 2
drivers/net/wireless/rtlwifi/rtl8192c/dm_common.c:892 rtl92c_dm_txpower_tracking_callback_thermalmeter() error: buffer overflow 'txpwr_level' 2 <= 2

The unreachable code message is fixed by deleting the code that follows a return.

The errors are fixed by increasing the size of txpwr_level.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>