mstarddc_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".

BUG=b:185191942
TEST=builds

Change-Id: Ia0e5f6879bfbfac591a40119ee3e0942a5cbc4b9
Signed-off-by: Anastasia Klimchuk <aklm@chromium.org>
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M mstarddc_spi.c
1 file changed, 38 insertions(+), 14 deletions(-)