feat(file system): add memory-based romfs

1, this RomFS's codebase is Nuttx romfs, then it is compatible with
Linux RomFS and you can create such a file system using the tool genromfs.
2, there are two major changes against with the original Nuttx romfs:
    1), it is memory-based: all contents of the fs are stored in the
        memory in the very first stage of "mount".
    2), this version of romfs is altered to be compatible with our new
        version of VFS to take advantage of vnode cache and path cache.

close: #I3S0CP

tools/build/mk/liteos_tables_ldflags.mk

@@ -146,6 +146,7 @@ LITEOS_TABLES_DRIVER_LDFLAGS := \
 ####FS MAP####
 LITEOS_TABLES_FSMAP_LDFLAGS := \
     -uramfs_fsmap \
+    -uromfs_fsmap \
     -unfs_fsmap \
     -ufat_fsmap \
     -ujffs_fsmap \

tools/build/mk/los_config.mk

@@ -325,6 +325,11 @@ ifeq ($(LOSCFG_FS_RAMFS), y)
     LIB_SUBDIRS     += fs/ramfs
 endif
 
+ifeq ($(LOSCFG_FS_ROMFS), y)
+    LITEOS_BASELIB  += -lromfs
+    LIB_SUBDIRS     += fs/romfs
+endif
+
 ifeq ($(LOSCFG_FS_NFS), y)
     LITEOS_BASELIB  += -lnfs
     LIB_SUBDIRS     += fs/nfs

tools/scripts/make_rootfs/rootfsimg.sh

@@ -38,6 +38,7 @@ JFFS2_TOOL=mkfs.jffs2
 WIN_JFFS2_TOOL=mkfs.jffs2.exe
 YAFFS2_TOOL=mkyaffs2image100
 VFAT_TOOL=mkfs.vfat
+ROMFS_TOOL=genromfs
 MCOPY_TOOL=mcopy
 
 tool_check() {
@@ -66,8 +67,11 @@ if [ "${FSTYPE}" = "jffs2" ]; then
         ${JFFS2_TOOL} -q -o ${ROOTFS_IMG} -d ${ROOTFS_DIR} --pagesize=4096
     fi
 elif [ "${FSTYPE}" = "yaffs2" ]; then
-        tool_check ${YAFFS2_TOOL}
-	${YAFFS2_TOOL}  ${ROOTFS_DIR} ${ROOTFS_IMG} 2k 24bit
+    tool_check ${YAFFS2_TOOL}
+    ${YAFFS2_TOOL}  ${ROOTFS_DIR} ${ROOTFS_IMG} 2k 24bit
+elif [ "${FSTYPE}" = "romfs" ]; then
+    tool_check ${ROMFS_TOOL}
+    ${ROMFS_TOOL}  -d ${ROOTFS_DIR} -f ${ROOTFS_IMG}
 elif [ "${FSTYPE}" = "vfat" ]; then
     if [ "${system}" != "Linux" ] ; then
         echo "Unsupported fs type!" >&2