rng: stm32: rename STM32 RNG driver

Rename the RNG driver as it is usable by other STM32 platforms
than the STM32MP1x ones. Rename CONFIG_RNG_STM32MP1 to
CONFIG_RNG_STM32

Signed-off-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
Reviewed-by: Grzegorz Szymaszek <gszymaszek@short.pl>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
diff --git a/configs/stm32mp15_basic_defconfig b/configs/stm32mp15_basic_defconfig
index dc491cf..ffc25ab 100644
--- a/configs/stm32mp15_basic_defconfig
+++ b/configs/stm32mp15_basic_defconfig
@@ -150,7 +150,7 @@
 CONFIG_DM_REGULATOR_STPMIC1=y
 CONFIG_REMOTEPROC_STM32_COPRO=y
 CONFIG_DM_RNG=y
-CONFIG_RNG_STM32MP1=y
+CONFIG_RNG_STM32=y
 CONFIG_DM_RTC=y
 CONFIG_RTC_STM32=y
 CONFIG_SERIAL_RX_BUFFER=y