writing_musb_glue_layer.rst: Fix broken URL

The http://processors.wiki.ti.com EOL in january 2021

The old documentation is still available through the wayback machine.

Signed-off-by: Richard Genoud <[email protected]>
Signed-off-by: Jonathan Corbet <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: richard-bootlin

Documentation/driver-api/usb/writing_musb_glue_layer.rst

@@ -717,4 +717,4 @@ https://www.maximintegrated.com/app-notes/index.mvp/id/1822
 :ref:`Writing USB Device Drivers <writing-usb-driver>`
 
 Texas Instruments USB Configuration Wiki Page:
-http://processors.wiki.ti.com/index.php/Usbgeneralpage
+https://web.archive.org/web/20201215135015/http://processors.wiki.ti.com/index.php/Usbgeneralpage