arm64: zynqmp: Enable MP by default via Kconfig

Simplify defconfig for ZynqMP but keep option not to enable it for mini
targets.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 3ba8efd..c7168e0 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -919,6 +919,7 @@
 	imply BOARD_LATE_INIT
 	imply CMD_DM
 	imply FAT_WRITE
+	imply MP
 
 config TEGRA
 	bool "NVIDIA Tegra"