dummyflasher.c: Get rid of get_data_from_context()

Relying on the global state 'dummy_buses_supported' to
determine the member master struct [mst.par or mst.spi]
is both buggy and ultimately unnecessary. It became
apparent after commit 4eef651ff503f81b77 just how fragile
this really was as the 'defaults' simultaneously selected
both buses causing get_data_from_context() to fall-though
however memory happened to workout by chance due to the
union. With the member master structs now being struct
fields the subtle bug is more apparent.

BUG=none
BRANCH=none
TEST=`./flashrom -r /tmp/fwupdater.apnSQQ -p dummy:emulate=VARIABLE_SIZE,image=test_update.sh.tmp.emu,size=8388608`

Change-Id: I07a34faf50ff0679cb3d6bc683142f82160010b1
Signed-off-by: Edward O'Callaghan <quasisec@google.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/54907
Reviewed-by: Anastasia Klimchuk <aklm@chromium.org>
Reviewed-by: Sam McNally <sammc@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
1 file changed