drivers: usb_dc_native_posix: Check data length before copy

Fail requests if the data does not fit inside buffer.

This commit only adds missing sanity checks but the native posix driver
remains broken at the design level. The amount of work to fix the native
posix driver in legacy USB stack is deemed too great to be worth it.

Coverity-CID: 195841, GitHub issue #58564
Coverity-CID: 240244, GitHub issue #58570

Signed-off-by: Tomasz Moń <tomasz.mon@nordicsemi.no>