SVD file cleanup

[austinglaser]

I've been playing around with the XMC4700 relax kit, and it seems like there's some cleanup to be done on the SVD. As a small example, the IOCRN registers in the PORTN peripherals have their fields enumerated as VALUE1 through VALUE9, rather than actual meaningful names.

I was going to do some cleanup here, but wanted to check in beforehand regarding what kinds of changes you'd accept. Are you OK with me directly editing the SVD file? I know some other PAC (e.g. https://github.com/japaric/stm32f30x) maintain a separate patch file which they apply to the SVD -- that would require a little more messing around in the build system, but should be doable as well.

[lucasbrendel]

Go ahead and just modify the files directly