[coreboot] [patch] Added dependency checking for the USB EHCI debug Kconfig option

[Cristi Magherusan]

See attached patch.

I had to add that ifdef because config.h didn't have defined the
CONFIG_USBDEBUG_DIRECT option and compilation failed.
If anyone has an idea how I can get it defined there, I'm all ears.

Signed-off-by: Cristi Magherusan