mwifiex: don't return zero on failure paths in mwifiex_pcie_init()

If pci_iomap() fails in mwifiex_pcie_init(), it breaks off initialization,
deallocates all resources, but returns zero.
The patch adds -EIO as return value in this case.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Acked-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>