fix some spelling typos found in kfigure.py

The origin comes from Masanari Iida [1] patching the Linux tree.

[1] https://www.mail-archive.com/linux-doc@vger.kernel.org/msg17614.html

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

linuxdoc/kfigure.py

@@ -81,7 +81,7 @@
 # -------------
 
 def which(cmd):
-    """Searches the ``cmd`` in the ``PATH`` enviroment.
+    """Searches the ``cmd`` in the ``PATH`` environment.
 
     This *which* searches the PATH for executable ``cmd`` . First match is
     returned, if nothing is found, ``None`` is returned.
@@ -419,7 +419,7 @@ def visit_kernel_render(self, node):
 
     tmp_ext = RENDER_MARKUP_EXT.get(srclang, None)
     if tmp_ext is None:
-        app.warn('kernel-render: "%s" unknow / include raw.' % (srclang))
+        app.warn('kernel-render: "%s" unknown / include raw.' % (srclang))
         return
 
     if not dot_cmd and tmp_ext == '.dot':
@@ -482,7 +482,7 @@ def build_node(self):
         srclang = self.arguments[0].strip()
         if srclang not in RENDER_MARKUP_EXT.keys():
             return [self.state_machine.reporter.warning(
-                'Unknow source language "%s", use one of: %s.' % (
+                'Unknown source language "%s", use one of: %s.' % (
                     srclang, ",".join(RENDER_MARKUP_EXT.keys())),
                 line=self.lineno)]