pci: Fix header type check

Header Type is 8-bit. The bit 7 is used to identify a multi-function
device. The lower bit 1 and bit 0 are used to identify the header type.

   00b is defined for Normal devices
   01b is defined for PCI-to-PCI bridges
   10b is defined for PC Card Standard

Fix the check by masking the lower 2 bits only.

This patch fixes the device probe on VMware Workstation.

Signed-off-by: Asias He <asias@cloudius-systems.com>