[ARM] Arrange for platforms to select appropriate CPU support

Rather than:

	config CPU_BLAH
		bool
		depends on ARCH_FOO || MACH_BAR
		default y if ARCH_FOO || MACH_BAR

arrange for ARCH_FOO and MACH_BAR to select CPU_BLAH directly.

Acked-by: Nicolas Pitre <nico@marvell.com>
Acked-by: Andrew Victor <linux@maxim.org.za>
Acked-by: Brian Swetland <swetland@google.com>
Acked-by: Eric Miao <eric.miao@marvell.com>
Acked-by: Nicolas Bellido <ml@acolin.be>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>