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/ls1012ardb_qspi_defconfig b/configs/ls1012ardb_qspi_defconfig
index b440881..4062134 100644
--- a/configs/ls1012ardb_qspi_defconfig
+++ b/configs/ls1012ardb_qspi_defconfig
@@ -16,6 +16,7 @@
 CONFIG_BOOTARGS="console=ttyS0,115200 root=/dev/ram0 earlycon=uart8250,mmio,0x21c0500 quiet lpj=250000"
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_CMD_GREPENV=y
+CONFIG_CMD_MEMTEST=y
 CONFIG_CMD_GPT=y
 CONFIG_CMD_I2C=y
 CONFIG_CMD_MMC=y