drm/bridge: analogix_dp: simplify and correct PLL lock checks

Move the wait loop into its own function, so it doesn't need to be
replicated in multiple locations. Also move the PLL lock checks between
setting the link bandwidth, which may cause the PLL to unlock, and the
MACRO_RST which needs the PLL to be locked.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Robert Foss <rfoss@kernel.org>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240619182200.3752465-12-l.stach@pengutronix.de