usb: device_next: accept padded Mass Storage CDBs

Universal Serial Bus Mass Storage Specification For Bootability requires
that device shall accept Bulk-Only-Transport bCBWCBLength of 12 for all
commands documented in the specification. Allow padding for commands
documented in Bootability specification, but leave others intact.

This fixes Request Sense on Windows 11 which previously failed due to
bCBWCBLength being 12 instead of 6.

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