ARM: Fix default CPU selection for ARCH_MULTI_V5

CPU_ARM926T should be selected if no other CPU is. Put the ! in the
right place so this works.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Fixes: 24e860fb

 ("ARM: multiplatform: always pick one CPU type")
Cc: stable@vger.kernel.org # v3.11+
Signed-off-by: Jason Cooper <jason@lakedaemon.net>