arm64: defconfig: Add M31 eUSB2 PHY config

arm64: defconfig: Add M31 eUSB2 PHY config

The Qualcomm SM8750 SoCs use an eUSB2 PHY driver different from the
already existing M31 USB driver because it requires a connection
to an eUSB2 repeater. Thus, for USB to probe and work properly on
the Qualcomm SM8750 SoCs, enable the additional driver.

Signed-off-by: Melody Olvera <melody.olvera@oss.qualcomm.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Jingyi Wang <jingyi.wang@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20251021-knp-usb-v2-4-a2809fffcfab@oss.qualcomm.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>