wd: use timeout_add_msec(9)

[Klemens Nanni]

In case of errors, wd(4) generally retries transfers after
hz / 2 [ticks] = 500 [ms].

Builds and boots, but (sadly) my PowerBook G4's disk is working fine so
this code has not been triggered.

OK?

Index: dev/ata/wd.c
===================================================================
RCS file: /cvs/src/sys/dev/ata/wd.c,v
retrieving revision 1.125
diff -u -p -r1.125 wd.c
--- dev/ata/wd.c        30 Dec 2017 23:08:29 -0000      1.125
+++ dev/ata/wd.c        6 Jul 2019 21:42:39 -0000
@@ -94,7 +94,7 @@
 
 #define        WDIORETRIES_SINGLE 4    /* number of retries before 
single-sector */
 #define        WDIORETRIES     5       /* number of retries before giving up */
-#define        RECOVERYTIME hz/2       /* time to wait before retrying a cmd */
+#define        RECOVERYTIME_MSEC 500   /* time to wait before retrying a cmd */
 
 #define DEBUG_INTR   0x01
 #define DEBUG_XFERS  0x02
@@ -555,7 +555,8 @@ retry:
                    wd->sc_wdc_bio.blkdone, wd->sc_dk.dk_label);
                if (wd->retries++ < WDIORETRIES) {
                        printf(", retrying\n");
-                       timeout_add(&wd->sc_restart_timeout, RECOVERYTIME);
+                       timeout_add_msec(&wd->sc_restart_timeout,
+                           RECOVERYTIME_MSEC);
                        return;
                }
                printf("\n");