Revert "bcmdhd: set off-screen PM mode to FAST"

I'll just save more power.

This reverts commit 3e1e9c10186c7d40170bab84b206a1833b2978af.

Signed-off-by: zwliew <zhaoweiliew@gmail.com>
bcmdhd: use PM_MAX instead of PM_FAST

This saves battery.

Signed-off-by: zwliew <zhaoweiliew@gmail.com>