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/drivers/acpi/resources/rscreate.c b/drivers/acpi/resources/rscreate.c
index c0bbfa2..08b8d73 100644
--- a/drivers/acpi/resources/rscreate.c
+++ b/drivers/acpi/resources/rscreate.c
@@ -124,7 +124,7 @@
  *
  * FUNCTION:    acpi_rs_create_pci_routing_table
  *
- * PARAMETERS:  package_object          - Pointer to an union acpi_operand_object
+ * PARAMETERS:  package_object          - Pointer to a union acpi_operand_object
  *                                        package
  *              output_buffer           - Pointer to the user's buffer
  *