vsprintf: add printk specifier %px

vsprintf: add printk specifier %px

printk specifier %p now hashes all addresses before printing. Sometimes
we need to see the actual unmodified address. This can be achieved using
%lx but then we face the risk that if in future we want to change the
way the Kernel handles printing of pointers we will have to grep through
the already existent 50 000 %lx call sites. Let's add specifier %px as a
clear, opt-in, way to print a pointer and maintain some level of
isolation from all the other hex integer output within the Kernel.

Add printk specifier %px to print the actual unmodified address.

Signed-off-by: Tobin C. Harding <me@tobin.cc>