zephyr: nrf_wifi: Update RPU patch to rev#e2b91b4ff86b

UMAC:
    [SHEL-3829] : Throughput drops at down range RVR.
    [SHEL-3877] : Channel 100 unsupported in SoftAP mode even if
                  regulatory domain supports it.
    [SHEL-3878] : WPS (PIN/PBC) connection issue where Auth event getting
                  dropped in RPU.
LMAC:
    Latest toolkit upgrade from 0.14.0 to 0.19.0.
    SQI changes.

Signed-off-by: Karun Kumar Eagalapati <[email protected]>

Author: karun2796