scripts/decode_stacktrace: match basepath using shell prefix operator, not regex

The basepath may contain special characters, which would confuse the regex
matcher.  ${var#prefix} does the right thing.

Link: http://lkml.kernel.org/r/20190518055946.181563-1-drinkcat@chromium.org
Fixes: 67a28de4 ("scripts/decode_stacktrace: only strip base path when a prefix of the path")
Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/decode_stacktrace.sh

@@ -85,7 +85,7 @@ parse_symbol() {
 	fi
 
 	# Strip out the base of the path
-	code=${code//^$basepath/""}
+	code=${code#$basepath/}
 
 	# In the case of inlines, move everything to same line
 	code=${code//$'\n'/' '}