compat: backport netif_set_real_num_rx_queues()

compat: backport netif_set_real_num_rx_queues()

netif_set_real_num_rx_queues() was added on v2.6.37 but
requires CONFIG_RPS support which was added on v2.6.35.
A few updates were done on the net core though to support
changing the number of RX queues if the device was already
registered. We can't support this on older kernels though
so the best we can do is for kernels >= 2.6.35 simply try
to update the num_rx_queues and if the device is registered
fail.

mcgrof@frijol ~/linux-next (git::master)$ git describe --contains 62fe0b40
v2.6.37-rc1~147^2~340

commit 62fe0b40abb3484413800edaef9b087a20059acf
Author: Ben Hutchings <bhutchings@solarflare.com>
Date:   Mon Sep 27 08:24:33 2010 +0000

    net: Allow changing number of RX queues after device allocation

    For RPS, we create a kobject for each RX queue based on the number of
    queues passed to alloc_netdev_mq().  However, drivers generally do not
    determine the numbers of hardware queues to use until much later, so
    this usually represents the maximum number the driver may use and not
    the actual number in use.

    For TX queues, drivers can update the actual number using
    netif_set_real_num_tx_queues().  Add a corresponding function for RX
    queues, netif_set_real_num_rx_queues().

    Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
mcgrof@drvbp1 ~/compat (git::master)$ time ckmake
Trying kernel 3.6.5-030605-generic [OK]
Trying kernel 3.5.7-030507-generic [OK]
Trying kernel 3.4.17-030417-generic [OK]
Trying kernel 3.3.8-030308-generic [OK]
Trying kernel 3.2.33-030233-generic [OK]
Trying kernel 3.1.10-030110-generic [OK]
Trying kernel 3.0.50-030050-generic [OK]
Trying kernel 2.6.39-02063904-generic [OK]
Trying kernel 2.6.38-02063808-generic [OK]
Trying kernel 2.6.37-02063706-generic [OK]
Trying kernel 2.6.36-02063604-generic [OK]
Trying kernel 2.6.35-02063513-generic [OK]
Trying kernel 2.6.34-02063413-generic [OK]
Trying kernel 2.6.33-02063320-generic [OK]
Trying kernel 2.6.32-02063260-generic [OK]
Trying kernel 2.6.31-02063113-generic [OK]
Trying kernel 2.6.30-02063010-generic [OK]
Trying kernel 2.6.29-02062906-generic [OK]
Trying kernel 2.6.28-02062810-generic [OK]
Trying kernel 2.6.27-020627-generic [OK]
Trying kernel 2.6.26-020626-generic [OK]
Trying kernel 2.6.25-020625-generic [OK]
Trying kernel 2.6.24-020624-generic [OK]

real    2m5.270s
user    8m51.501s
sys     2m1.576s

Signed-off-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>