make_dev_ssd: Allow smaller kernel partition.

Some Brillo devices may have smaller kernel partition and we need to reduce the
size limit.

BUG=none
BRANCH=none
TEST=make_dev_ssd.sh applied on a Brillo config with 8MB kernel partition.

Change-Id: I9ca37445a6cdb20138f13dbe975c207383a1474c
Reviewed-on: https://chromium-review.googlesource.com/255341
Tested-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-by: Mao Huang <littlecvr@chromium.org>
Commit-Queue: Hung-Te Lin <hungte@chromium.org>
diff --git a/scripts/image_signing/make_dev_ssd.sh b/scripts/image_signing/make_dev_ssd.sh
index b5e9d7e..bfd4e4a 100755
--- a/scripts/image_signing/make_dev_ssd.sh
+++ b/scripts/image_signing/make_dev_ssd.sh
@@ -136,7 +136,7 @@
   local ssd_device="$1"
 
   # reasonable size for current kernel partition
-  local min_kernel_size=32000
+  local min_kernel_size=16000
   local max_kernel_size=65536
   local resigned_kernels=0