obmc-phosphor-image: Don't build .cpio.lzma.u-boot

For most incremental builds, the critical path is generating a new
installed obmc-phosphor-image fs, then compressing it to put into a
.lzma.u-boot container. However, the latter step doesn't seem necessary
except for the out-of-kernel initrd (obmc-phosphor-initramfs) because
obmc-phosphor-image is packaged as a squashfs-xz and not seen by U-Boot.

qemu.inc has its own IMAGE_FSTYPE appends, so qemuarm builds should not
be affected.

This reduces incremental build time by about a third, when doing
'bitbake obmc-phosphor-image' with no changes.
before:
150.74s user 66.01s system 148% cpu 2:25.96 total
after:
94.78s user 64.87s system 159% cpu 1:39.97 total

This reflects the removal of the single-threaded, CPU-bound 'lzma'
invocation from the critical path.

Netbootable images can still by generated by adding:
  IMAGE_FSTYPES += "cpio.${INITRAMFS_CTYPE}.u-boot"

to local.conf.

Signed-off-by: Xo Wang <xow@google.com>
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
Change-Id: I867500589ffe0a36cbe1193843907d7882239227
diff --git a/meta-phosphor/conf/machine/include/obmc-bsp-common.inc b/meta-phosphor/conf/machine/include/obmc-bsp-common.inc
index 2cbdd89..648eb93 100644
--- a/meta-phosphor/conf/machine/include/obmc-bsp-common.inc
+++ b/meta-phosphor/conf/machine/include/obmc-bsp-common.inc
@@ -10,7 +10,6 @@
 
 MACHINEOVERRIDES =. "openbmc:"
 
-IMAGE_FSTYPES += "cpio.${INITRAMFS_CTYPE}.u-boot"
 IMAGE_FSTYPES += "${@bb.utils.contains('DISTRO_FEATURES', \
         'obmc-ubi-fs', \
         'mtd-ubi mtd-ubi-tar', \