wifi: softirq: reduce ksoftirqd scheduled rate to improve TCP throughtput

wifi: softirq: reduce ksoftirqd scheduled rate to improve TCP throughtput

PD#162113: improve ap62x8 rx tput

The reason why wifi TCP rx throughtput lower than kernel3.14 are as flollows:
On K3.14, RX has more time to work in ISR, but on K4.9, RX has more time to
work in kernel ksoftirqd thread, however, ksoftirqd has a very low priority.

On K4.9, a commit from upstream caused this difference, then revert it.

Revert "softirq: Let ksoftirqd do its job"

This reverts commit 4cd13c21b207e80ddb1144c576500098f2d5f882.

Change-Id: I094232dad5dfddbcd94c35ec42a5e3302ed52459
Signed-off-by: libo <bo.li@amlogic.com>