MAINTAINERS: Update platform-drivers-x86 maintainer and tree

Update the general entry for drivers/platform/x86 with myself as
maintainer and point to my tree.

Leave Matthew Garrett as maintainer of the two drivers called out
specifically elsewhere in MAINTAINERS.

Signed-off-by: Darren Hart <[email protected]>
Cc: Matthew Garrett <[email protected]>
1 file changed