clk: microchip: mpfs: make the rtc's ahb clock critical

The onboard RTC's AHB bus clock must be kept running as the RTC will
stop & lose track of time if the AHB interface clock is disabled.

Fixes: 635e5e73 ("clk: microchip: Add driver for Microchip PolarFire SoC")
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20220909123123.2699583-3-conor.dooley@microchip.com

drivers/clk/microchip/clk-mpfs.c

@@ -375,6 +375,8 @@ static const struct clk_ops mpfs_periph_clk_ops = {
  *   trap handler
  * - CLK_MMUART0: reserved by the hss
  * - CLK_DDRC: provides clock to the ddr subsystem
+ * - CLK_RTC: the onboard RTC's AHB bus clock must be kept running as the rtc will stop
+ *   if the AHB interface clock is disabled
  * - CLK_FICx: these provide the processor side clocks to the "FIC" (Fabric InterConnect)
  *   clock domain crossers which provide the interface to the FPGA fabric. Disabling them
  *   causes the FPGA fabric to go into reset.
@@ -399,7 +401,7 @@ static struct mpfs_periph_hw_clock mpfs_periph_clks[] = {
 	CLK_PERIPH(CLK_CAN0, "clk_periph_can0", PARENT_CLK(AHB), 14, 0),
 	CLK_PERIPH(CLK_CAN1, "clk_periph_can1", PARENT_CLK(AHB), 15, 0),
 	CLK_PERIPH(CLK_USB, "clk_periph_usb", PARENT_CLK(AHB), 16, 0),
-	CLK_PERIPH(CLK_RTC, "clk_periph_rtc", PARENT_CLK(AHB), 18, 0),
+	CLK_PERIPH(CLK_RTC, "clk_periph_rtc", PARENT_CLK(AHB), 18, CLK_IS_CRITICAL),
 	CLK_PERIPH(CLK_QSPI, "clk_periph_qspi", PARENT_CLK(AHB), 19, 0),
 	CLK_PERIPH(CLK_GPIO0, "clk_periph_gpio0", PARENT_CLK(AHB), 20, 0),
 	CLK_PERIPH(CLK_GPIO1, "clk_periph_gpio1", PARENT_CLK(AHB), 21, 0),