mtd: afs: fix build warning

drivers/mtd/afs.c:244: warning: format ‘%5d’ expects type ‘int’, but argument 4 has type ‘uint64_t’

[dwmw2: fix incorrect 'KB' too]
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>