arm64: defconfig: Drop duplicate CONFIG_OMAP_USB2 entry

arm64: defconfig: Drop duplicate CONFIG_OMAP_USB2 entry

CONFIG_OMAP_USB2 is already enabled as a module in the default defconfig
since commit 8a703a728a745 ("arm64: defconfig: Enable USB2 PHY Driver").
Remove the duplicate entry to fix the following warning:

    arch/arm64/configs/defconfig:1705:warning: override: reassigning to symbol OMAP_USB2

Fixes: 91fe3315cdf9f ("arm64: defconfig: Enable missing AMD/Xilinx drivers")
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20251015150728.118296-1-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Michal Simek <michal.simek@amd.com>