phy: lynx-28g: common lynx_pll_get()

phy: lynx-28g: common lynx_pll_get()

The logic should be absolutely unchanged in the new 10G Lynx SerDes
driver, so let's move this to phy-fsl-lynx-core.c and update the 28G
Lynx driver to use the common variant.

While at it, update the call site, lynx_28g_lane_remap_pll(), to use the
new data structures, and refactor the NULL pll pointer check (the
current form triggers a checkpatch CHECK).

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://patch.msgid.link/20260610151952.2141019-6-vladimir.oltean@nxp.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>