cmd: Toggle the default value of CONFIG_CMD_IMLS

Having this as a 'default y' is rather annoying because it doesn't
actually compile unless other options are defined in the board header:

../cmd/bootm.c: In function 'do_imls_nor':
../cmd/bootm.c:330:7: error: 'CONFIG_SYS_MAX_FLASH_BANKS' undeclared (first use in this function); did you mean 'CONFIG_SYS_MAX_FLASH_SECT'?
   i < CONFIG_SYS_MAX_FLASH_BANKS; ++i, ++info) {

Make it 'default n' so people who develop new boards that start from a
blank defconfig have one less compilation failure to debug.

Signed-off-by: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
diff --git a/configs/ls1046aqds_lpuart_defconfig b/configs/ls1046aqds_lpuart_defconfig
index 17a53ef..6efa766 100644
--- a/configs/ls1046aqds_lpuart_defconfig
+++ b/configs/ls1046aqds_lpuart_defconfig
@@ -10,6 +10,7 @@
 CONFIG_BOOTARGS="console=ttyS0,115200 root=/dev/ram0 earlycon=uart8250,mmio,0x21c0500 mtdparts=60000000.nor:2m@0x100000(nor_bank0_uboot),40m@0x1100000(nor_bank0_fit),7m(nor_bank0_user),2m@0x4100000(nor_bank4_uboot),40m@0x5100000(nor_bank4_fit),-(nor_bank4_user);7e800000.flash:4m(nand_uboot),36m(nand_kernel),472m(nand_free);spi0.0:2m(uboot),14m(free)"
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y
+CONFIG_CMD_IMLS=y
 CONFIG_CMD_GREPENV=y
 CONFIG_CMD_MEMINFO=y
 CONFIG_CMD_MEMTEST=y