Replace sprintf()->snprintf() and strcpy()->strlcpy()

The strcpy() and sprintf() functions are deprecated on some platforms.
Care is needed to ensure correct size is used.  If some platforms
miss snprintf, we can add a #define to sprintf, likewise strlcpy().

The biggest change is adding a size parameter to zfs_id_to_fuidstr().

The various *_impl_get() functions are only used on linux and have
not yet been updated.

Reviewed by: Sean Eric Fagan <sef@ixsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Jorgen Lundman <lundman@lundman.net>
Closes #10400

module/icp/algs/modes/gcm.c

@@ -843,7 +843,7 @@ gcm_impl_init(void)
 		    sizeof (gcm_fastest_impl));
 	}
 
-	strcpy(gcm_fastest_impl.name, "fastest");
+	strlcpy(gcm_fastest_impl.name, "fastest", GCM_IMPL_NAME_MAX);
 
 #ifdef CAN_USE_GCM_ASM
 	/*
@@ -955,7 +955,7 @@ gcm_impl_set(const char *val)
 	return (err);
 }
 
-#if defined(_KERNEL)
+#if defined(_KERNEL) && defined(__linux__)
 
 static int
 icp_gcm_impl_set(const char *val, zfs_kernel_param_t *kp)