swtpm_setup: remove redundant delete_state function

swtpm_setup: remove redundant delete_state function

...and use delete_swtpm_statefiles instead. This function iterates the
folder instead of just deleting one file, but since it is already called
before the init call guarded here, it can only affect files created by
this run anyway.

Note that delete_state had slightly different return semantics, but it
doesn't matter, as the return value is ignored here anyway (best effort
cleanup).

Signed-off-by: Stefan Reiter <stefan@pimaker.at>