docs(linux): J742S2: Update the USB documentation

All the J7 family SoCs share same USB documentation. This documentation
is incorrect in the case of J742S2 EVM. Update the documentation for
J742S2 EVM by adding 'J742S2' as a "CONFIG_part_variant" in the USB
documentation for J784S4 EVM as same documentation is valid for both
the platforms.

Signed-off-by: Hrushikesh Salunke <[email protected]>

Author: hrushikesh221

source/linux/Foundational_Components/Kernel/Kernel_Drivers/USB/CDNS3.rst

@@ -41,7 +41,7 @@ EVM
     USB2 controller is not present on J721E SoC so micro-AB 3.0 connector is not
     usable.
 
-.. ifconfig:: CONFIG_part_variant in ('J784S4')
+.. ifconfig:: CONFIG_part_variant in ('J784S4, J742S2')
 
    The following diagram depicts USB integration in |__PART_FAMILY_DEVICE_NAMES__| EVM.