[usb-f103] Use the "modern" /rcc include instead of f1.

The f103 usb core should be usable on the l1 as well, and the /f1/rcc
isn't explicitly required anymore.  This is an important change to be
able to share the driver.
[stm32-l1] Include f103 usb driver in build.

Tested with the h103 cdcacm demo (originally targetting an F103) on a
custom L1 based board and it enumerates successfully.