scsi: lpfc: Add dependency on CPU_FREQ

Since commit 317aeb8 ("scsi: lpfc: Add blk_io_poll support for latency
improvment"), the lpfc driver depends on CPUFREQ. Without it, builds fail
with

drivers/scsi/lpfc/lpfc_sli.c: In function 'lpfc_init_idle_stat_hb':
drivers/scsi/lpfc/lpfc_sli.c:7329:26: error:
	implicit declaration of function 'get_cpu_idle_time'

Add the missing dependency.

Link: https://lore.kernel.org/r/20200722023027.36866-1-linux@roeck-us.net
Fixes: 317aeb8 ("scsi: lpfc: Add blk_io_poll support for latency improvment")
Cc: Dick Kennedy <dick.kennedy@broadcom.com>
Cc: James Smart <jsmart2021@gmail.com>
Reviewed-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/Kconfig

@@ -1154,6 +1154,7 @@ source "drivers/scsi/qedf/Kconfig"
 config SCSI_LPFC
 	tristate "Emulex LightPulse Fibre Channel Support"
 	depends on PCI && SCSI
+	depends on CPU_FREQ
 	depends on SCSI_FC_ATTRS
 	depends on NVME_TARGET_FC || NVME_TARGET_FC=n
 	depends on NVME_FC || NVME_FC=n