This is where the other debug_memory_* functions are declared, so let's
move it here for symmetry.
This allows us to drop an include of u_debug_gallium.h, which makes us
depend on gallium-headers in non-gallium code.
Reviewed-by: Eric Anholt <eric@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3901>