GitLab

Adapts pico-sdk clocks_init() into clocks_init_optional_usb() which takes
an argument to initialise USB clocks or not.

To avoid a code size increase the SDK clocks_init() function is linker
wrapped to become clocks_init_optional_usb(true).

This work was funded through GitHub Sponsors.
Signed-off-by: Angus Gratton <angus@redyak.com.au>