brcmfmac: increase max hanger slots from 1K to 3K in fws layer

Will enable FMAC to push more packets to bus tx queue and help
improve throughput when fws queuing is enabled. This change is
required to tune the throughput for passing WMM CERT tests.

Signed-off-by: Madhan Mohan R <madhanmohan.r@cypress.com>
Signed-off-by: Chi-hsien Lin <chi-hsien.lin@cypress.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1585124429-97371-5-git-send-email-chi-hsien.lin@cypress.com