[POWERPC] maple: Use platform name in define_machine()

Prevailing practice for define_machine() in powerpc is to use the
platform name when the platform has only one define_machine()
statement, but maple uses "maple_md".  This caused me some
head-scratching when writing some new code that uses
machine_is(maple).

Use "maple" instead of "maple_md".  There should not be any behavioral
change -- fixup_maple_ide() calls machine_is(maple) but the body of
the function is ifdef'd out.
Signed-off-by: Nathan Lynch <ntl@pobox.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/platforms/maple/setup.c

@@ -319,7 +319,7 @@ static int __init maple_probe(void)
 	return 1;
 }
 
-define_machine(maple_md) {
+define_machine(maple) {
 	.name			= "Maple",
 	.probe			= maple_probe,
 	.setup_arch		= maple_setup_arch,