HID: core: increase HID report buffer size to 8KiB

We have a HID touch device that reports its opens and shorts test
results in HID buffers of size 8184 bytes. The maximum size of the HID
buffer is currently set to 4096 bytes, causing probe of this device to
fail. With this patch we increase the maximum size of the HID buffer to
8192 bytes, making device probe and acquisition of said buffers succeed.

Signed-off-by: Johan Korsnes <jkorsnes@cisco.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Armando Visconti <armando.visconti@st.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>