default or selected kernelversion does not have config value CONFIG_USB_MUSB_AM35X.
Result is shown for kernelversion 6.9.9

AM35x

modulename: am35x.ko

configname: CONFIG_USB_MUSB_AM35X

Linux Kernel Configuration
└─>Device Drivers
└─>USB support
└─>AM35x
In linux kernel since version 2.6.37 (release Date: 2011-01-04)  
source code:
drivers/usb/musb/am35x.c