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/T2080RDB_defconfig b/configs/T2080RDB_defconfig
index 2eb4910..adda021 100644
--- a/configs/T2080RDB_defconfig
+++ b/configs/T2080RDB_defconfig
@@ -10,6 +10,7 @@
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_IMLS=y
 CONFIG_CMD_MEMTEST=y
+CONFIG_SYS_ALT_MEMTEST=y
 CONFIG_CMD_I2C=y
 CONFIG_CMD_MMC=y
 CONFIG_CMD_SF=y