mwifiex: pcie: Fix memory leak in mwifiex_pcie_alloc_cmdrsp_buf

In mwifiex_pcie_alloc_cmdrsp_buf, a new skb is allocated which should be
released if mwifiex_map_pci_memory() fails. The release is added.

Fixes: fc331460 ("mwifiex: use pci_alloc/free_consistent APIs for PCIe")
Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
Acked-by: Ganapathi Bhat <gbhat@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>