raiden_debug_spi.c: Adds context states and helper functions

Adds context states to handle the read and write buffers as transmit
and receive states. These are used to keep track of the number of
bytes transmitted and received allowing future support of multi-packet
messages in the v2 protocol.

Adds context states to handle the USB packets, these allow us to
simplify the process of loading data from the transmit buffer
into a USB packets' data section and from a USB packet to it's
receive buffers. These will also keep track of the size of the USB
packet allowing a simpler interface to transmit them.

Helper functions have been added to help with copying data between
the transmit and receive context states to and from the USB packets.

BUG=b:139058552
BRANCH=none
TEST=Manual testing of ServoMicro and Flashrom when performing
    reads, writes, and verification of the EC firmware on Nami.
TEST=Builds

Signed-off-by: Brian J. Nemec <bnemec@chromium.com>
Change-Id: Ic6eea82ffc604ec56278f7aaa0deafe0cf75973c
---
M raiden_debug_spi.c
1 file changed, 324 insertions(+), 108 deletions(-)