Change AST and AACRAID drivers to be modules instead of built-in

This patch changes the config files in order to make AST and AACRAID
drivers built as modules on Petitboot, instead of built-in.

Those drivers showed some issues lately that would've been
'workarounded' if both were modules, so we could blacklist
them. The total increase in BOOTKERNEL image is less than
80 kbytes.

Signed-off-by: Guilherme G. Piccoli <gpiccoli@linux.vnet.ibm.com>
diff --git a/openpower/configs/linux/skiroot_p9_defconfig b/openpower/configs/linux/skiroot_p9_defconfig
index 9884909..1c6a4c5 100644
--- a/openpower/configs/linux/skiroot_p9_defconfig
+++ b/openpower/configs/linux/skiroot_p9_defconfig
@@ -87,7 +87,7 @@
 CONFIG_SCSI_CXGB3_ISCSI=m
 CONFIG_SCSI_CXGB4_ISCSI=m
 CONFIG_SCSI_BNX2_ISCSI=m
-CONFIG_SCSI_AACRAID=y
+CONFIG_SCSI_AACRAID=m
 CONFIG_MEGARAID_NEWGEN=y
 CONFIG_MEGARAID_MM=m
 CONFIG_MEGARAID_MAILBOX=m
@@ -157,7 +157,7 @@
 # CONFIG_I2C_HELPER_AUTO is not set
 CONFIG_DRM=y
 CONFIG_DRM_RADEON=y
-CONFIG_DRM_AST=y
+CONFIG_DRM_AST=m
 CONFIG_FIRMWARE_EDID=y
 CONFIG_FB_MODE_HELPERS=y
 CONFIG_FB_OF=y