meta-ibm: Move Tacoma and Rainier to eMMC u-boot config

The AST2600 systems booted from NOR during bringup, but now that we have
eMMC support in u-boot they can run from eMMC.

Signed-off-by: Joel Stanley <joel@jms.id.au>
Change-Id: I7734dcc95162b6fddb4bf93dcf9286178cbe0adf
diff --git a/conf/machine/rainier.conf b/conf/machine/rainier.conf
index 3fe43f3..9c1a7a4 100644
--- a/conf/machine/rainier.conf
+++ b/conf/machine/rainier.conf
@@ -1,5 +1,5 @@
 KERNEL_DEVICETREE = "aspeed-bmc-ibm-rainier.dtb"
-UBOOT_MACHINE = "ast2600_openbmc_spl_defconfig"
+UBOOT_MACHINE = "ast2600_openbmc_spl_emmc_defconfig"
 UBOOT_DEVICETREE = "ast2600-rainier"
 SPL_BINARY = "spl/u-boot-spl.bin"