drivers/clock_control: stm32 g0, g4, l4, remove get_pllout_frequency()

After replacing STM32_SRC_PLLCLK by the STM32_SRC_PLL_x sources
this function is no longer needed and are therefore removed.

Also, those functions returned a wrong frequency.
They should have used get_pllsrc_frequency() instead of get_pll_source()
to get the input frequency.

Signed-off-by: Thomas Stranger <thomas.stranger@outlook.com>
diff --git a/drivers/clock_control/clock_stm32g0.c b/drivers/clock_control/clock_stm32g0.c
index 266e12f..5055835 100644
--- a/drivers/clock_control/clock_stm32g0.c
+++ b/drivers/clock_control/clock_stm32g0.c
@@ -65,19 +65,6 @@
 	LL_RCC_PLL_EnableDomain_SYS();
 }
 
-
-/**
- * @brief Return pllout frequency
- */
-__unused
-uint32_t get_pllout_frequency(void)
-{
-	return __LL_RCC_CALC_PLLCLK_FREQ(get_pll_source(),
-					 pllm(STM32_PLL_M_DIVISOR),
-					 STM32_PLL_N_MULTIPLIER,
-					 pllr(STM32_PLL_R_DIVISOR));
-}
-
 #endif /* defined(STM32_PLL_ENABLED) */
 
 /**
diff --git a/drivers/clock_control/clock_stm32g4.c b/drivers/clock_control/clock_stm32g4.c
index dfd4c7d..779498a 100644
--- a/drivers/clock_control/clock_stm32g4.c
+++ b/drivers/clock_control/clock_stm32g4.c
@@ -69,18 +69,6 @@
 	LL_RCC_PLL_EnableDomain_SYS();
 }
 
-/**
- * @brief Return pllout frequency
- */
-__unused
-uint32_t get_pllout_frequency(void)
-{
-	return __LL_RCC_CALC_PLLCLK_FREQ(get_pll_source(),
-					 pllm(STM32_PLL_M_DIVISOR),
-					 STM32_PLL_N_MULTIPLIER,
-					 pllr(STM32_PLL_R_DIVISOR));
-}
-
 #endif /* defined(STM32_PLL_ENABLED) */
 
 /**
diff --git a/drivers/clock_control/clock_stm32l4_l5_wb_wl.c b/drivers/clock_control/clock_stm32l4_l5_wb_wl.c
index 2949cd4..9bad636 100644
--- a/drivers/clock_control/clock_stm32l4_l5_wb_wl.c
+++ b/drivers/clock_control/clock_stm32l4_l5_wb_wl.c
@@ -84,18 +84,6 @@
 	LL_RCC_PLL_EnableDomain_SYS();
 }
 
-/**
- * @brief Return pllout frequency
- */
-__unused
-uint32_t get_pllout_frequency(void)
-{
-	return __LL_RCC_CALC_PLLCLK_FREQ(get_pll_source(),
-					 pllm(STM32_PLL_M_DIVISOR),
-					 STM32_PLL_N_MULTIPLIER,
-					 pllr(STM32_PLL_R_DIVISOR));
-}
-
 #endif /* defined(STM32_PLL_ENABLED) */
 
 /**