iwlwifi: dvm: fix flush support for old firmware

iwlwifi: dvm: fix flush support for old firmware

Since the commit below, iwldvm sends the FLUSH command to
the firmware. All the devices that use iwldvm have a
firmware that expects the _v3 version of this command,
besides 5150.
5150's latest available firmware still expects a _v2 version
of the FLUSH command.
This means that since the commit below, we had a mismatch for
this specific device only.
This mismatch led to the NMI below:

Loaded firmware version: 8.24.2.2
Start IWL Error Log Dump:
Status: 0x0000004C, count: 5
0x00000004 | NMI_INTERRUPT_WDG
0x000006F4 | uPc
0x000005BA | branchlink1
0x000006F8 | branchlink2
0x000008C2 | interruptlink1
0x00005B02 | interruptlink2
0x00000002 | data1
0x07030000 | data2
0x00000068 | line
0x3E80510C | beacon time
0x728A0EF4 | tsf low
0x0000002A | tsf hi
0x00000000 | time gp1
0x01BDC977 | time gp2
0x00000000 | time gp3
0x00010818 | uCode version
0x00000000 | hw version
0x00484704 | board version
0x00000002 | hcmd
0x2FF23080 | isr0
0x0103E000 | isr1
0x0000001A | isr2
0x1443FCC3 | isr3
0x11800112 | isr4
0x00000068 | isr_pref
0x000000D4 | wait_event
0x00000000 | l2p_control
0x00000007 | l2p_duration
0x00103040 | l2p_mhvalid
0x00000007 | l2p_addr_match
0x00000000 | lmpm_pmg_sel
0x00000000 | timestamp
0x00000200 | flow_handler

This was reported here:
https://bugzilla.kernel.org/show_bug.cgi?id=88961

Cc: <stable@vger.kernel.org>
Fixes: a0855054e59b ("iwlwifi: dvm: drop non VO frames when flushing")
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>