wl12xx: update PLT initialization for new firmware

In revision > 6.1.3.0.0 the firmware expects memory configuration command
as part of boot. This was missing if driver boots in PLT mode.
The patch adds the memory configuration command, which fixes PLT commands
tx continuous and rx statistics.

Signed-off-by: Gery Kahn <geryk@ti.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>