docs: Grammar and spelling fixes

Signed-off-by: Ville Skyttä <ville.skytta@iki.fi>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 20180612065150.21110-1-ville.skytta@iki.fi
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
diff --git a/docs/qemupciserial.inf b/docs/qemupciserial.inf
index 6f7eef4..7ca7667 100644
--- a/docs/qemupciserial.inf
+++ b/docs/qemupciserial.inf
@@ -1,7 +1,7 @@
 ; qemupciserial.inf for QEMU, based on MSPORTS.INF
 
 ; The driver itself is shipped with Windows (serial.sys).  This is
-; just a inf file to tell windows which pci id the serial pci card
+; just an inf file to tell windows which pci id the serial pci card
 ; emulated by qemu has, and to apply a name tag to it which windows
 ; will show in the device manager.