treewide: Migrate CONFIG_SYS_ALT_MEMTEST to Kconfig

Migrate the CONFIG_SYS_ALT_MEMTEST option to Kconfig.

Signed-off-by: Mario Six <mario.six@gdsys.cc>
[trini: Re-run migration after also including CMD_MEMTEST]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/xilinx_zynqmp_zc1751_xm015_dc1_defconfig b/configs/xilinx_zynqmp_zc1751_xm015_dc1_defconfig
index 1125ebd..a9052b4 100644
--- a/configs/xilinx_zynqmp_zc1751_xm015_dc1_defconfig
+++ b/configs/xilinx_zynqmp_zc1751_xm015_dc1_defconfig
@@ -24,6 +24,7 @@
 CONFIG_FASTBOOT_FLASH_MMC_DEV=0
 CONFIG_CMD_THOR_DOWNLOAD=y
 CONFIG_CMD_MEMTEST=y
+CONFIG_SYS_ALT_MEMTEST=y
 CONFIG_CMD_CLK=y
 CONFIG_CMD_DFU=y
 # CONFIG_CMD_FLASH is not set