wifi: rtw89: Fix clang -Wimplicit-fallthrough in rtw89_query_sar()

clang warns (or errors with CONFIG_WERROR=y):

  drivers/net/wireless/realtek/rtw89/sar.c:216:3: error: unannotated fall-through between switch labels [-Werror,-Wimplicit-fallthrough]
    216 |                 case RTW89_TAS_STATE_DPR_FORBID:
        |                 ^
  drivers/net/wireless/realtek/rtw89/sar.c:216:3: note: insert 'break;' to avoid fall-through
    216 |                 case RTW89_TAS_STATE_DPR_FORBID:
        |                 ^
        |                 break;
  1 error generated.

Clang is a little more pedantic than GCC, which does not warn when
falling through to a case that is just break or return. Clang's version
is more in line with the kernel's own stance in deprecated.rst, which
states that all switch/case blocks must end in either break,
fallthrough, continue, goto, or return. Add the missing break to silence
the warning.

Closes: https://github.com/ClangBuiltLinux/linux/issues/1921
Fixes: eb2624f55a ("wifi: rtw89: Introduce Time Averaged SAR (TAS) feature")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230822-rtw89-tas-clang-implicit-fallthrough-v1-1-5cb73f0fa976@kernel.org

drivers/net/wireless/realtek/rtw89/sar.c

@@ -211,6 +211,7 @@ s8 rtw89_query_sar(struct rtw89_dev *rtwdev, u32 center_freq)
 		case RTW89_TAS_STATE_DPR_ON:
 			delta = rtw89_txpwr_tas_to_sar(sar_hdl, tas->delta);
 			cfg -= delta;
+			break;
 		case RTW89_TAS_STATE_DPR_FORBID:
 		default:
 			break;