brcmfmac: enable frameburst mode in default firmware setting

The frameburst feature can enable per-packet framebursting in firmware
side and get higher TX throughput in High Throughput(HT) mode. To enhance
TX throughput, we enable frameburst mode in default firmware setting.

Signed-off-by: Wright Feng <wright.feng@cypress.com>
Acked-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>