ARM: prima2: remove redundant select CPU_V7

<linux@armlinux.org.uk>, Barry Song <baohua@kernel.org>,
linux-kernel@vger.kernel.org

ARCH_ATLAS7 resides in "if ARCH_SIRF ... end", and ARCH_SIRF depends
on ARCH_MULTI_V7, which selects CPU_V7.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Olof Johansson <olof@lixom.net>