refactor(st-clock): support deactivated STGEN in stm32mp_stgen_config

Update function stm32mp_stgen_config() to support deactivated STGEN
when frequency is 0, for example on STOP2 exit for STM32MP25.

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Change-Id: Id371c4602a614bbfa0ecc7ce2d2e0ac5261e1d52
diff --git a/drivers/st/clk/stm32mp_clkfunc.c b/drivers/st/clk/stm32mp_clkfunc.c
index 28ddb73..ed1f8a7 100644
--- a/drivers/st/clk/stm32mp_clkfunc.c
+++ b/drivers/st/clk/stm32mp_clkfunc.c
@@ -350,9 +350,11 @@
 	}
 
 	mmio_clrbits_32(STGEN_BASE + CNTCR_OFF, CNTCR_EN);
-	counter = stm32mp_stgen_get_counter() * rate / cntfid0;
 
-	stgen_set_counter(counter);
+	if (cntfid0 != 0U) {
+		counter = stm32mp_stgen_get_counter() * rate / cntfid0;
+		stgen_set_counter(counter);
+	}
 	mmio_write_32(STGEN_BASE + CNTFID_OFF, rate);
 	mmio_setbits_32(STGEN_BASE + CNTCR_OFF, CNTCR_EN);