ACPI: EC: add leading zeros to debug messages

Add leading zeros to pr_debug() calls. For example if x=0x0a, the format
"0x%2x" will result the string "0x a", the format "0x%2.2x" will result "0x0a".

Signed-off-by: Márton Németh <nm127@freemail.hu>
Signed-off-by: Len Brown <len.brown@intel.com>