target/linux/*/base-files/lib/upgrade/platform.sh - wrong check for ARGC

target/linux/*/base-files/lib/upgrade/platform.sh - wrong check for ARGC

ARGC is a 'C-ism', but not known/valid in shell-syntax - insert the correct
var $# (=number of args) here. under normal conditions this had no impact,
but we should at least correct it. the error was observable like this:

root@box:~ [ -e "/etc/functions.sh" ] && . /etc/functions.sh
root@box:~ [ -e "/lib/functions.sh" ] && . /lib/functions.sh
root@box:~ . /lib/upgrade/platform.sh
root@box:~ . /lib/upgrade/common.sh
root@box:~ platform_check_image /tmp/myfirmware.bin
ash: bad number
root@box:~ echo $?
0

Signed-off-by: Bastian Bittorf <bittorf@bluebottle.com>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@40915 3c298f89-4303-0410-b956-a3cf2f4a3e73