ARM: socfpga: Fix A10 SoCDK Kconfig

The Kconfig checked for SoCFPGA Arria10 as a platform, instead of
checking for specific board configuration, which works with one
single platform in tree, but not with multiple. Fix it.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Chin Liang See <chin.liang.see@intel.com>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
Cc: Tien Fong Chee <tien.fong.chee@intel.com>

board/altera/arria10-socdk/Kconfig

@@ -1,4 +1,4 @@
-if TARGET_SOCFPGA_ARRIA10
+if TARGET_SOCFPGA_ARRIA10_SOCDK
 
 config SYS_CPU
 	default "armv7"