raiden_debug_spi.c: Clean up global state

The Chromium flashrom fork has very poor dispatch logic whereas
upstream has proper inversion of control with a generic 'data'
void * member to stuff long-lived state in. Leverage the member
to store the USB descriptor state in during the life-time of the
spi master.

V.2: Remove unnecessary indirection as is the case in
  commit a25c13cd.

BUG=b:140394053
BRANCH=none
TEST=builds && detects flashchip name.

Change-Id: Ida9dce97fef2c6dfd68a278c879917fdd3ff7fef
Signed-off-by: Edward O'Callaghan <quasisec@google.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/40105


Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Sam McNally <sammc@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>