libpayload: Drop usb_fatal()

libpayload: Drop usb_fatal()

We have fatal(), which is just as good.

Coccinelle script:
  @@
  expression E;
  @@
  -usb_fatal(E)
  +fatal(E)

Change-Id: Iabecbcc7d068cc0f82687bf51d89c2626642cd86
Signed-off-by: Patrick Georgi <patrick.georgi@secunet.com>
Reviewed-on: http://review.coreboot.org/395
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Tested-by: build bot (Jenkins)