arm: socfpga: Move Stratix10 and Agilex to use TARGET_SOCFPGA_SOC64

Create common macro TARGET_SOCFPGA_SOC64 for Stratix10 and Agilex.

Signed-off-by: Siew Chin Lim <elly.siew.chin.lim@intel.com>
diff --git a/drivers/fpga/Kconfig b/drivers/fpga/Kconfig
index 425b52a..dc0b3dd 100644
--- a/drivers/fpga/Kconfig
+++ b/drivers/fpga/Kconfig
@@ -33,7 +33,7 @@
 
 config FPGA_INTEL_SDM_MAILBOX
 	bool "Enable Intel FPGA Full Reconfiguration SDM Mailbox driver"
-	depends on TARGET_SOCFPGA_STRATIX10 || TARGET_SOCFPGA_AGILEX
+	depends on TARGET_SOCFPGA_SOC64
 	select FPGA_ALTERA
 	help
 	  Say Y here to enable the Intel FPGA Full Reconfig SDM Mailbox driver