ARM: 5951/1: ARM: fix documentation of the PrimeCell bus

This fixes the filepath encoded in <linux/amba/bus.h> and adds
some documentation as to what this bus really means.
Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

include/linux/amba/bus.h

 /*
- *  linux/include/asm-arm/hardware/amba.h
+ *  linux/include/amba/bus.h
+ *
+ *  This device type deals with ARM PrimeCells and anything else that
+ *  presents a proper CID (0xB105F00D) at the end of the I/O register
+ *  region or that is derived from a PrimeCell.
  *
  *  Copyright (C) 2003 Deep Blue Solutions Ltd, All Rights Reserved.
  *