phy: qcom-qmp: Utilize fully-specified DT registers

Utilize the newly fixed up DT bindings to get the tx2 and rx2 register
regions for the second lane of dual-lane PHYs. Before this change,
the driver was simply using lane one's register region and adding
0x400, which reached well beyond the DT-specified register
allocation. This would have been a crash were it not for the page size
on ARM64. Fix the driver not to rely on the magic of virtual memory by
using the newly specified DT register regions for tx2 and rx2.

In order to support existing device trees, this change also contains a
fallback mode for when those new register regions don't exist, which
reverts to the original behavior of overreaching and prints a complaint.

Signed-off-by: Evan Green <evgreen@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>