dummyflasher.c: Move 'spi_write_256_chunksize' into emu_data

Move 'spi_write_256_chunksize' out of global scope and
into the emu_data reentrent struct.

BUG=none
BRANCH=none
TEST=builds

Change-Id: I633f4df4bd47e661cd69801f21910b667899d505
Signed-off-by: Edward O'Callaghan <quasisec@google.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/54721
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
1 file changed