Squashed commit of the following:
drivers/usbhost/usbhost_max3421e.c: Add USB tracing support. Fix compilation errors when assertions and debug is enabled.
drivers/usbhost/usbhost_max3421e.c: Fixes to get a clean compilation.
drivers/usbhost/usbhost_max3421e.c: Drivers is basically code complete.
drivers/usbhost/usbhost_max3421e.c: Missed a little bit of logic in the last commit.
drivers/usbhost/usbhost_max3421e.c: Completes implementatin of control transfers.
drivers/usbhost/usbhost_max3421e.c: Implements low-level part of packet receive.
drivers/usbhost/usbhost_max3421e.c: Reorder some functions add a little more transfer-related logic.
drivers/usbhost/usbhost_max3421e.c: Completes basic logic path for sending normal packets.
drivers/usbhost/usbhost_max3421e.c: Correct handling of SNDFIFO double buffering.
drivers/usbhost/usbhost_max3421e.c: Not necessary to set the ACKSTAT bit in host mode. Clean up some comments.
drivers/usbhost/usbhost_max3421e.c: Mostly cosmetic cleanup
drivers/usbhost/usbhost_max3421e.c: Revise some previous logic. Looks like the MAX3421E can handle 16 channels in host mode. A little bit of work on packet transfer logic.
Copy paste error fix
drivers/usbhost/usbhost_max3421e.c: Add some channel allocation logic.
drivers/usbhost/usbhost_max3421e.c: Add some initialization logic.
drivers/usbhost/usbhost_max3421e.c: Add logic to determine if a full or low speed device has been connected.
drivers/usbhost/usbhost_max3421e.c: Add interrupt handling and bus reset logic.
drivers/usbhost/usbhost_max3421e.c: Add framework for an MAX3421E host driver. Initial commit is just the STM32 OTGFS host driver with a few new SPI-related functions.
