Revert "memory-hotplug: add 0x prefix to HEX block_size_bytes"

This reverts commit ba168fc3.

It changes user-visible sysfs interfaces, and breaks some existing user
space applications which apparently rely on the fact that the output
does not contain the "0x" prefix.

Requested-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>