lib: vsprintf: Add %pa format specifier for phys_addr_t types

Add the %pa format specifier for printing a phys_addr_t
type and its derivative types (such as resource_size_t),
since the physical address size on some platforms can vary
based on build options, regardless of the native integer
type.

Change-Id: I2ba0003d689a9a2bd13f1a1e2d897b6eacc5d224
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>