of: Reimplement of_machine_is_compatible() using of_machine_compatible_match()

of_machine_compatible_match() works with a table of strings.
of_machine_is_compatible() is a simplier version with only one string.

Re-implement of_machine_is_compatible() by setting a table of strings
with a single string then using of_machine_compatible_match().

Suggested-by: Rob Herring <robh+dt@kernel.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231214103152.12269-3-mpe@ellerman.id.au