scripts: west_commands: nrfjprog: Add support for --qspiini

Allow for users to provide a --qspiini parameter that is passed directly to
the nrfjprog executable but only in the --program operation. This is
required since e073210e enabled the
-O/--tool-opt for all operations, but --qspiini is only allowed combined
with --program.

Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>