wic: Add utility function for parsing sourceparams

Parses strings of the form key1=val1[,key2=val2,...] and returns a
dict.  Also accepts valueless keys i.e. without =.

(From OE-Core rev: 36f258ee6e60c26fd44b9bc71c318363cec71f42)

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/wic/utils/oe/misc.py

@@ -179,3 +179,26 @@ def get_bitbake_var(key):
             val = get_line_val(line, key)
             return val
     return None
+
+def parse_sourceparams(sourceparams):
+    """
+    Split sourceparams string of the form key1=val1[,key2=val2,...]
+    into a dict.  Also accepts valueless keys i.e. without =.
+
+    Returns dict of param key/val pairs (note that val may be None).
+    """
+    params_dict = {}
+
+    params = sourceparams.split(',')
+    if params:
+        for p in params:
+            if not p:
+                continue
+            if not '=' in p:
+                key = p
+                val = None
+            else:
+                key, val = p.split('=')
+            params_dict[key] = val
+
+    return params_dict