ACPI: remove superfluous NULL pointer check from acpi_processor_get_throttling_info()

Dan's list contains:

drivers/acpi/processor_throttling.c +1139 acpi_processor_get_throttling_info(11) warning: variable derefenced before check 'pr'

acpi_processor_get_throttling_info() is never called with pr == NULL.

[ bart: the potential NULL pointer dereference was finally fixed in
  (much later than mine) commit 5cfa245 but my patch is still valid ]

Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/processor_throttling.c

@@ -1133,9 +1133,6 @@ int acpi_processor_get_throttling_info(struct acpi_processor *pr)
 	int result = 0;
 	struct acpi_processor_throttling *pthrottling;
 
-	if (!pr)
-		return -EINVAL;
-
 	ACPI_DEBUG_PRINT((ACPI_DB_INFO,
 			  "pblk_address[0x%08x] duty_offset[%d] duty_width[%d]\n",
 			  pr->throttling.address,