stm32mp1: fix reference for STMicroelectronics

Replace reference to the correct name STMicroelectronics

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Heiko Schocher <hs@denx.de>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>