read_msix_capability previously read the whole config file unbounded
(pc hang: the config char device never EOF'd at the time) and then
returned None unconditionally. Now it reads at most 256 bytes (the
standard capability chain region) and parses the chain for real:
status bit, cap list walk, MSI-X (0x11) message-control table size.
Includes base submodule bump for the pcid config EOF fix.
vasilito
e230dfaa3d