[config] enable romfs

This change enables the use of the romfs filesystem, an extremely simple
format usable with build-time image generation using the fuchsia
toolchain.

Test: ran virtmagma* tests via new romfs disk
Change-Id: I3a018f4906e72798da2c03dbb6d8acf3b240ff7c
diff --git a/arch/arm64/configs/machina_defconfig b/arch/arm64/configs/machina_defconfig
index edc331fd..b088b90 100644
--- a/arch/arm64/configs/machina_defconfig
+++ b/arch/arm64/configs/machina_defconfig
@@ -26,4 +26,5 @@
 CONFIG_VIRTIO_INPUT=y
 CONFIG_EXT2_FS=y
 CONFIG_EXT4_FS=y
+CONFIG_ROMFS_FS=y
 CONFIG_TMPFS=y
diff --git a/arch/x86/configs/machina_defconfig b/arch/x86/configs/machina_defconfig
index 53d424c..6547cbf 100644
--- a/arch/x86/configs/machina_defconfig
+++ b/arch/x86/configs/machina_defconfig
@@ -355,6 +355,7 @@
 CONFIG_FUSE_FS=y
 CONFIG_FSCACHE=y
 CONFIG_PROC_KCORE=y
+CONFIG_ROMFS_FS=y
 CONFIG_TMPFS=y
 CONFIG_TMPFS_POSIX_ACL=y
 CONFIG_SQUASHFS=y