[fdt] Allow paths and aliases to be terminated with separator characters

[fdt] Allow paths and aliases to be terminated with separator characters

Non-permitted name characters such as a colon are sometimes used to
separate alias names or paths from additional metadata, such as the
baud rate for a UART in the "/chosen/stdout-path" property.

Support the use of such alias names and paths by allowing any
character not permitted in a property name to terminate a property or
node name match.  (This is a very relaxed matching rule that will
produce false positive matches on invalid input, but this is unlikely
to cause problems in practice.)

Signed-off-by: Michael Brown <mcb30@ipxe.org>