dt-bindings: clk: mpfs: add defines for two new clocks

The RTC reference and MSSPLL were previously not documented or defined,
as they were unused. Add their defines to the PolarFire SoC header.

Fixes: 2145bb68 ("dt-bindings: clk: microchip: Add Microchip PolarFire host binding")
Reviewed-by: Daire McNamara <daire.mcnamara@microchip.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20220413075835.3354193-6-conor.dooley@microchip.comAcked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

include/dt-bindings/clock/microchip,mpfs-clock.h

 /* SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) */
 /*
  * Daire McNamara,<daire.mcnamara@microchip.com>
- * Copyright (C) 2020 Microchip Technology Inc.  All rights reserved.
+ * Copyright (C) 2020-2022 Microchip Technology Inc.  All rights reserved.
  */
 
 #ifndef _DT_BINDINGS_CLK_MICROCHIP_MPFS_H_
@@ -42,4 +42,7 @@
 #define CLK_ATHENA	31
 #define CLK_CFM		32
 
+#define CLK_RTCREF	33
+#define CLK_MSSPLL	34
+
 #endif	/* _DT_BINDINGS_CLK_MICROCHIP_MPFS_H_ */