drivers: staging: rtl8188eu: core: rtw_security: Fix misspelled word

This patch fixes the checkpatch.pl warning:

WARNING: 'halfs' may be misspelled - perhaps 'halves'?

Signed-off-by: Ioana Ciornei <ciorneiioana@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>