Marvell/Drivers: MvPhyDxe: Remove MvHwDescLib.h dependency

Finally, after switching to new MV_BOARD_DESC solution
in all drivers, stop using MvHwDescLib.h by its last user
and safely remove this header.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Marcin Wojtas <mw@semihalf.com>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>