MAINTAINERS: Add x86 early-quirks.c file pattern to PCI subsystem

arch/x86/kernel/early-quirks.c contains special PCI quirks that need to
run even before the usual DECLARE_PCI_FIXUP_EARLY() quirks.  These have
typically been merged by the x86 maintainers, which is fine, but PCI folks
should at least see what's happening, so add a file pattern to the PCI
subsystem entry.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Ingo Molnar <mingo@kernel.org>