Fixed RP2xxx usb reset register masks

[eugenepentland]

Before the rework on resets.zig the mask had all of the rp2xxx hal/resets.zig Mask had all of the values in the packed struct as false by default, so when reset.reset(.{pll_usb}) was run, it would make a bitmask for only that register. But now it makes a bitmask for every register and takes all pins out of reset mode.

I just made it so it gets the bit offset of the register and creates a bitmask for only the register in question. This should support rp2040 and rp2350, but currently is only tested with the usb cdc example on the rp2040.

[eugenepentland]

Turns out controlling those reset bits aren't needed because in reset.masks, it sets the usbctrl and pll_usb to be on by default.

[arkadiuszwojcik]

@eugenepentland I can confirm this fix works. This resolves: #261

CC: @r4gus @haydenridd