mem_ap: fix format of logged addresses

mem_ap: fix format of logged addresses

The macro TARGET_ADDR_FMT, defined in helper/types.h, already
includes the prefix "0x" in front of the hexadecimal number,
being defined as:
	#define TARGET_ADDR_FMT "0x%8.8" TARGET_PRIxADDR
An additional "0x" is present in mem_ap; it prints debug messages
with a double "0x" before the address:
	Debug: 2921 34180 mem_ap.c:153 mem_ap_write_memory():
	Writing memory at physical address 0x0x5000000c; size 4;
	count 1

Remove the incorrect hexadecimal prefix.

Change-Id: I38f19ed2a2f542bd5df53e947a2604f1cbe80e08
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/5222
Tested-by: jenkins
Reviewed-by: Matthias Welwarsky <matthias@welwarsky.de>