dm: core: Add DM_FLAG_PROBE_AFTER_BIND flag

Introduce DM_FLAG_PROBE_AFTER_BIND flag, which can be set by driver or
uclass in .bind(), to indicate such driver instance should be probe()d
once binding of all devices is complete.

This is useful in case the driver determines that hardware initialization
is mandatory on boot, and such initialization happens only in probe().
This also solves the inability to call device_probe() from .bind().

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Patrice Chotard <patrice.chotard@foss.st.com>
Cc: Patrick Delaunay <patrick.delaunay@foss.st.com>
Cc: Sean Anderson <seanga2@gmail.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Steven Lawrance <steven.lawrance@softathome.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
Tested-by: Patrice Chotard <patrice.chotard@foss.st.com>