trivial: fix an -> a typos in documentation and comments

It is always "an" if there is a vowel _spoken_ (not written).
So it is:
"an hour" (spoken vowel)
but
"a uniform" (spoken 'j')

Signed-off-by: Frederik Schwarzer <schwarzerf@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/Documentation/laptops/thinkpad-acpi.txt b/Documentation/laptops/thinkpad-acpi.txt
index 71f0fe1..898b498 100644
--- a/Documentation/laptops/thinkpad-acpi.txt
+++ b/Documentation/laptops/thinkpad-acpi.txt
@@ -1475,7 +1475,7 @@
 
 0x020100:	Marker for thinkpad-acpi with hot key NVRAM polling
 		support.  If you must, use it to know you should not
-		start an userspace NVRAM poller (allows to detect when
+		start a userspace NVRAM poller (allows to detect when
 		NVRAM is compiled out by the user because it is
 		unneeded/undesired in the first place).
 0x020101:	Marker for thinkpad-acpi with hot key NVRAM polling