usb: Rename the config to "charger" in charger mode

init.usb.configfs.rc has the same trigger condition of midi function.
Rename the config name to "charger" to avoid triggerring twice of the
midi function.

Bug: 188744218
Test: USB enumerated in charger mode
Signed-off-by: Kyle Tso <kyletso@google.com>
Change-Id: Ica112fb4be66356901f6d5f21b79b9e648d49f35
1 file changed