The make rpm target depends on proper UTS_MACHINE definition.  Also, use
the variable in arch/arm64/kernel/setup.c, so that it's not accidentally
removed in the future.
Reported-and-tested-by: NFabian Vogt <fvogt@suse.com>
Signed-off-by: NMichal Marek <mmarek@suse.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>