reduce number of supported RA to only those that is tested

Author: hathach

README.rst

@@ -51,7 +51,7 @@ The stack supports the following MCUs:
 - **Renesas:**
 
 	- RX Series: 63N, 65N, 72N
-	- RA Series: RA2A1, RA2E1, RA2E2, RA2l1, RA4E1, RA4M1, RA4M2, RA4M3, RA4W1, RA6E1, RA6M1, RA6M2, RA6M3, RA6M4, RA6M5, RA6T1, RA6T2
+	- RA Series: RA4M1, RA4M3
 
 - **Silabs:** EFM32GG
 - **Sony:** CXD56