scripts: fix wrong usage of '==' operator

scripts: fix wrong usage of '==' operator

[base-files] shell-scripting: fix wrong usage of '==' operator

normally the '==' is used for invoking a regex parser and is a bashism.
all of the fixes just want to compare a string. the used busybox-ash
will silently "ignore" this mistake, but make it portable/clean at least.

this patch does not change the behavior/logic of the scripts.

Signed-off-by: Bastian Bittorf <bittorf@bluebottle.com>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@42911 3c298f89-4303-0410-b956-a3cf2f4a3e73