net: cnss2: Do not free DMA memory for FW segments till rmmod

System will do cold boot calibration on the first boot, which will save
calibration data to the DMA allocated memory. But once the wlan mode be
changed to mission mode, cnss2 will free all memory segments.

So do not free DMA allocated memory in cnss_pci_remove path and free only
in rmmod path.

Change-Id: I0423ec490231336c173a76936fe45b547b49b5d3
Signed-off-by: Miaoqing Pan <quic_miaoqing@quicinc.com>