qcacld-3.0: Set TX & RX NSS separately using vendor_attr

The vendor command QCA_WLAN_VENDOR_ATTR_CONFIG_NSS can
only be used to symmetricly set NSS configuration such
as 1x1 or 2x2.
So, use QCA_WLAN_VENDOR_ATTR_CONFIG_TX_NSS and
QCA_WLAN_VENDOR_ATTR_CONFIG_RX_NSS attributes to
configure the asymmetric NSS configuration (such as 1X2).
These attributes are used to dynamically configure the
number of spatial streams used for transmitting and
receiving the data. When configured in the disconnected
state, the configured value will be considered for
the following connection attempt.
If the NSS is updated after the connection, the updated
NSS value is notified to the peer using the Operating
Mode Notification/Spatial Multiplexing Power Save frame.
The value configured after the connection shall not be
greater than the value negotiated during the connection.
Any such higher value configuration shall be treated as
invalid configuration by the driver. These attribute
shall be configured together to define the symmetric
configuration (such as 2X2 or 1X1) or the asymmetric
configuration (such as 1X2).
If QCA_WLAN_VENDOR_ATTR_CONFIG_NSS attribute is also
provided along with these attributes then the driver
will update the TX and RX NSS based on
QCA_WLAN_VENDOR_ATTR_CONFIG_TX_NSS and
QCA_WLAN_VENDOR_ATTR_CONFIG_RX_NSS.

Change-Id: I85adb1fcfb2df5cf42eabd4f18b403b698767f42
CRs-Fixed: 2831416