wifi: ath12k: fix memory leak in ath12k_pci_remove()

In the Linux kernel, the following vulnerability has been resolved:

wifi: ath12k: fix memory leak in ath12k_pci_remove()

Kmemleak reported this error:

unreferenced object 0xffff1c165cec3060 (size 32):

comm "insmod", pid 560, jiffies 4296964570 (age 235.596s)

backtrace:

[<000000005434db68>] __kmem_cache_alloc_node+0x1f4/0x2c0

[<000000001203b155>] kmalloc_trace+0x40/0x88

[<0000000028adc9c8>] _request_firmware+0xb8/0x608

[<00000000cad1aef7>] firmware_request_nowarn+0x50/0x80

[<000000005011a682>] local_pci_probe+0x48/0xd0

[<00000000077cd295>] pci_device_probe+0xb4/0x200

[<0000000087184c94>] really_probe+0x150/0x2c0

The firmware memory was allocated in ath12k_pci_probe(), but not

freed in ath12k_pci_remove() in case ATH12K_FLAG_QMI_FAIL bit is

set. So call ath12k_fw_unmap() to free the memory.

Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.2.0-02280-QCAHMTSWPL_V1.0_V2.0_SILICONZ-1