MAINTAINERS: move USB gadget and phy entries under the main USB entry

MAINTAINERS: move USB gadget and phy entries under the main USB entry

Felipe has done a wonderful job over the years, but now it makes sense
to just maintain all of the USB stack in one tree.  Do so by removing
the current USB gadget and phy entries so that all portions of the stack
are now covered by the main USB maintainer entry.

Acked-by: Felipe Balbi <balbi@kernel.org>
Link: https://lore.kernel.org/r/20220930114041.1306711-1-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>