ARM: omap2plus: Drop unneeded select of MIGHT_HAVE_CACHE_L2X0

Support for TI AM43x SoCs depends on ARCH_MULTI_V7, which selects
ARCH_MULTI_V6_V7.
As the latter selects MIGHT_HAVE_CACHE_L2X0, there is no need for
SOC_AM43XX to select MIGHT_HAVE_CACHE_L2X0.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Tony Lindgren <tony@atomide.com>
Cc: linux-omap@vger.kernel.org
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>