usbblaster_spi.c: Refactor singleton states into reentrant pattern

Move global singleton states into a struct and store within
the spi_master data field for the life-time of the driver.

This is one of the steps on the way to move spi_master data
memory management behind the initialisation API, for more
context see other patches under the same topic "register_master_api".

This patch also introduces shutdown function for usbblaster, because
there was none previously and without shutdown function there is no
way to free spi_master data at the end of driver lifecycle.

BUG=b:185191942
TEST=builds

Change-Id: Ia81f9f40c7eab430a8b304d0b197ce7c75bf5ace
Signed-off-by: Anastasia Klimchuk <aklm@chromium.org>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/54044
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
1 file changed