MAINTAINERS: staging: westbridge: Delete section

commit 78f23926 ("Staging: delete westbridge code")
deleted the files, delete the section.

CC: David Cross <odc@cypress.com>
CC: Greg Kroah-Hartman <gregkh@suse.de>

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>