bcm53xx: calculate Seama MD5 using content of kernel partition

We don't want checksum to cover any part of UBI as even its part with
SquashFS may be changed due to e.g. flash wearing.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>

target/linux/bcm53xx/base-files/etc/uci-defaults/09_fix_crc

@@ -3,5 +3,5 @@
 kernel_size=$(sed -n 's/mtd[0-9]*: \([0-9a-f]*\).*"\(kernel\|linux\)".*/\1/p' /proc/mtd)
 
 mtd ${kernel_size:+-c 0x$kernel_size} fixtrx firmware && exit 0
-mtd fixseama firmware && exit 0
+mtd ${kernel_size:+-c 0x$kernel_size} fixseama firmware && exit 0
 exit 1