cpu/stm32*/ldscripts: remove all stm32 family linker scripts

cpu/stm32f3/ldscripts/stm32f302r8.ld

cpu/stm32f3/ldscripts/stm32f303k8.ld

cpu/stm32f3/ldscripts/stm32f303re.ld

cpu/stm32f3/ldscripts/stm32f303vc.ld

cpu/stm32f3/ldscripts/stm32f303ze.ld

cpu/stm32f3/ldscripts/stm32f334r8.ld

cpu/stm32f4/ldscripts/stm32f401re.ld

cpu/stm32f4/ldscripts/stm32f407vg.ld

cpu/stm32f4/ldscripts/stm32f410rb.ld

cpu/stm32f4/ldscripts/stm32f411re.ld

cpu/stm32f4/ldscripts/stm32f412zg.ld

cpu/stm32f4/ldscripts/stm32f413vg.ld

cpu/stm32f4/ldscripts/stm32f413zh.ld

cpu/stm32f4/ldscripts/stm32f415rg.ld

cpu/stm32f4/ldscripts/stm32f429zi.ld

cpu/stm32f4/ldscripts/stm32f446re.ld

cpu/stm32f4/ldscripts/stm32f446ze.ld

cpu/stm32f7/ldscripts/stm32f722ze.ld

cpu/stm32f7/ldscripts/stm32f746zg.ld

cpu/stm32f7/ldscripts/stm32f767zi.ld