mwifiex: avoid [-Wmaybe-uninitialized] warnings in pcie.c

drivers/net/wireless/mwifiex/pcie.c:1157:9: warning:
  'desc2' may be used uninitialized in this function
  [-Wmaybe-uninitialized]
drivers/net/wireless/mwifiex/pcie.c:1048:31: note:
  'desc2' was declared here

drivers/net/wireless/mwifiex/pcie.c:1159:9: warning:
  'desc' may be used uninitialized in this function
  [-Wmaybe-uninitialized]
drivers/net/wireless/mwifiex/pcie.c:1047:32: note:
  'desc' was declared here

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>