drivers/i2s_ll_stm32.c: pass proper PLLR param when setting I2S PLL
drivers/i2s_ll_stm32.c: pass proper PLLR param when setting I2S PLL

The PLLR parameter in LL_RCC_PLLI2S_ConfigDomain_I2S() API should
be selected among the following list of (already shifted) values:

  *         @arg @ref LL_RCC_PLLI2SR_DIV_2
  *         @arg @ref LL_RCC_PLLI2SR_DIV_3
  *         @arg @ref LL_RCC_PLLI2SR_DIV_4
  *         @arg @ref LL_RCC_PLLI2SR_DIV_5
  *         @arg @ref LL_RCC_PLLI2SR_DIV_6
  *         @arg @ref LL_RCC_PLLI2SR_DIV_7

This commit fixes PR #12609.

Signed-off-by: Armando Visconti <d93ca24ded08d03c3aa60af6d2fd0eb7ce54da11@st.com>

ldts/zephyr,finikorg/zephyr,nashif/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,nashif/zephyr,galak/zephyr,galak/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,nashif/zephyr,nashif/zephyr,nashif/zephyr,ldts/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,Vudentz/zephyr,finikorg/zephyr,galak/zephyr,explora26/zephyr,galak/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,galak/zephyr,explora26/zephyr,finikorg/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,ldts/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr