useradd-staticids: fix typo for '--expiredate'

useradd-staticids: fix typo for '--expiredate'

There is a typo in the useradd-staticids.bbclass that
causes error during do_install.

If build was configured to use usedadd-staticids and
the recipe included (for example):

USERADD_PARAM_${PN} = "--expiredate '' testUser"

Due to the typo this added the wrong option '--expiredata '
that caused an error.

Signed-off-by: Peter Bergin <peter@berginkonsult.se>
Signed-off-by: Ross Burton <ross.burton@intel.com>