staging: rtl8188eu: don't duplicate ieee80211 WLAN_HT_CAP_SM_PS_* constants

linux/ieee80211.h already defines constants for spatial multiplexing
power save modes.  Remove the duplicated definitions.

Signed-off-by: Jakub Sitnicki <jsitnicki@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>