memblock: Cast phys_addr_t to unsigned long long for printf use

phys_addr_t is not necessarily the same thing as unsigned long long.
It is, however, easier to cast it to unsigned long long for printf
purposes than it is to deal with differnent printf formats.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/4E1F4D2C.3000507@zytor.com