arm64: setup: report ELF_PLATFORM as the machine for utsname

uname -m reports the machine field from the current utsname, which should
reflect the endianness of the system.

This patch reports ELF_PLATFORM for the field, so that everything appears
consistent from userspace.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/setup.c

@@ -119,7 +119,7 @@ static void __init setup_processor(void)
 	printk("CPU: %s [%08x] revision %d\n",
 	       cpu_name, read_cpuid_id(), read_cpuid_id() & 15);
 
-	sprintf(init_utsname()->machine, "aarch64");
+	sprintf(init_utsname()->machine, ELF_PLATFORM);
 	elf_hwcap = 0;
 }