common: Add 0x prefix to phys mem addr printf conversion specifier

Signed-off-by: Carlos Rafael Giani <dv@pseudoterminal.org>
common: Add GstImxFDObject for reference counted file descriptors

Useful if the same file descriptor is used in several places, to ensure
it isn't closed prematurely

Signed-off-by: Carlos Rafael Giani <dv@pseudoterminal.org>