qcacld-3.0: Increase ll_stats driver buffer size

Currently driver allocates buffer of size 10KB which is
getting filled completely in some cases when size of
ll_stats is more than 10KB. Because of this driver
ignores some of the stats and user space does not
get the complete stats.

To address this issue increase the size of the buffer
to 12 KB.

Change-Id: I8c5500545a3c69ecb5ba3b1bb3e7f3338a61714f
CRs-Fixed: 2279495