Previously, there was no specific stm32f4r5.svd in lib/stm32-svd,
just stm32f4x5.svd was used; now, both files are present. This means
that the existing build-tag stm32f4r5 will include the
device/stm32/stm32f4r5.go file, and the additional build-tag stm32f4x5
would include the device/stm32/stm32f4x5.go file as well, resulting
in build conflicts. Renaming just the tag, which is used in src/machine,
and src/runtime, into stm32f4y5 solves this issue.