phy: ti: phy-j721e-wiz.c: Add usxgmii support in wiz driver

Changes the wiz_p_mac_div_sel() and wiz_mode_select() to
configure serdes for USXGMII.

Adds the support to configure mac_src_sel, refclk_sel and
rxfclk_sel in the LANECTL register and configures the serdes for
usxgmii.

[rogerq] Fix MAC_SRC_SEL to 0x3 for USXGMII as per CSL code.

Signed-off-by: Tanmay Patil <t-patil@ti.com>
Signed-off-by: Roger Quadros <rogerq@kernel.org>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>