x86/apm: Fix spelling mistake: "caculate" -> "calculate"

Trivial fix to spelling mistake in module parameter description text

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: kernel-janitors@vger.kernel.org
Cc: "H . Peter Anvin" <hpa@zytor.com>
Link: https://lkml.kernel.org/r/20180428092448.6493-1-colin.king@canonical.com

arch/x86/kernel/apm_32.c

@@ -2446,7 +2446,7 @@ MODULE_PARM_DESC(idle_threshold,
 	"System idle percentage above which to make APM BIOS idle calls");
 module_param(idle_period, int, 0444);
 MODULE_PARM_DESC(idle_period,
-	"Period (in sec/100) over which to caculate the idle percentage");
+	"Period (in sec/100) over which to calculate the idle percentage");
 module_param(smp, bool, 0444);
 MODULE_PARM_DESC(smp,
 	"Set this to enable APM use on an SMP platform. Use with caution on older systems");