docs: trace: coresight: coresight-etm4x-reference.rst: replace some characters

The conversion tools used during DocBook/LaTeX/html/Markdown->ReST
conversion and some cut-and-pasted text contain some characters that
aren't easily reachable on standard keyboards and/or could cause
troubles when parsed by the documentation build system.

Replace the occurences of the following characters:

	- U+00a0 (' '): NO-BREAK SPACE
	  as it can cause lines being truncated on PDF output
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/b6a04e881bc80a3c1d3d23ccbc8208ca3c9053fd.1623826294.git.mchehab+huawei@kernel.orgSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/trace/coresight/coresight-etm4x-reference.rst

@@ -427,7 +427,7 @@ the ‘TRC’ prefix.
 :Syntax:
     ``echo idx > vmid_idx``
 
-    Where idx <  numvmidc
+    Where idx <  numvmidc
 
 ----