rtlwifi: fix -Wpointer-sign warning

[ Upstream commit ef41937631bfee855e2b406e1d536efdaa9ce512 ]

There are thousands of warnings in a W=2 build from just one file:

drivers/net/wireless/realtek/rtlwifi/rtl8821ae/table.c:3788:15: warning: pointer targets in initialization of 'u8 *' {aka 'unsigned char *'} from 'char *' differ in signedness [-Wpointer-sign]

Change the types to consistently use 'const char *' for the
strings.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20201026213040.3889546-6-arnd@kernel.org


Stable-dep-of: 117dbeda22ec ("wifi: rtlwifi: Fix global-out-of-bounds bug in _rtl8812ae_phy_set_txpower_limit()")
Signed-off-by: Sasha Levin <sashal@kernel.org>