meta-google: Fix tcpdump append

When searching the tree for 'gmbc', I was surprised to find we had no
machines that use the Google layer. That's because it's a typo, and the
layer is called gbmc.

Change-Id: I75f31456f5e48246fe387322c72301d8552ca2d2
Signed-off-by: Joel Stanley <joel@jms.id.au>
diff --git a/meta-google/recipes-phosphor/images/obmc-phosphor-image.bbappend b/meta-google/recipes-phosphor/images/obmc-phosphor-image.bbappend
index 931a159..88a40d1 100644
--- a/meta-google/recipes-phosphor/images/obmc-phosphor-image.bbappend
+++ b/meta-google/recipes-phosphor/images/obmc-phosphor-image.bbappend
@@ -18,7 +18,7 @@
 # Include these useful utilities for all gbmc platforms
 OBMC_IMAGE_EXTRA_INSTALL:append:gbmc = " ipmitool"
 OBMC_IMAGE_EXTRA_INSTALL:append:gbmc = " lrzsz"
-OBMC_IMAGE_EXTRA_INSTALL:append:gmbc:dev = " tcpdump"
+OBMC_IMAGE_EXTRA_INSTALL:append:gbmc:dev = " tcpdump"
 
 # Add gBMC update recipes
 OBMC_IMAGE_EXTRA_INSTALL:append:gbmc = " dummy-gbmc-update"