rtw88: Add kernel 6.18 support and clean up patch logic (#9041)

- Created patch/misc/rtw88/6.18/ directory with upstream driver patches
- Removed obsolete kernel 6.16 reference from patch conditions
- Updated comment to clarify that RF path detection fix is only needed
  for kernel 6.1.x (upstreamed in 6.18+)

This fixes RTL8822CS WiFi initialization failures on kernel 6.18 where
the driver was not being properly patched due to missing version directory.

Fixes SDIO timeout errors during chip initialization.

lib/functions/compilation/patch/drivers_network.sh

@@ -366,8 +366,8 @@ driver_rtw88() {
 		fi
 	fi
 
-	if linux-version compare "${version}" eq 6.1 || linux-version compare "${version}" eq 6.16; then
-		process_patch_file "${SRC}/patch/misc/rtw88/hack/004-rtw88-sdio-rf-path-detection-fix.patch" "applying" # This patch has been tested only on kernel 6.1.x/6.16.x.
+	if linux-version compare "${version}" eq 6.1; then
+		process_patch_file "${SRC}/patch/misc/rtw88/hack/004-rtw88-sdio-rf-path-detection-fix.patch" "applying" # This patch is only for kernel 6.1.x. Not needed for 6.18+ (already upstream)
 	fi
 }