tests/sys/ztimer_overhead: mention auto_adjust in README and fix typos

Author: mguetschow

tests/sys/ztimer_overhead/README.md

@@ -22,3 +22,7 @@ ZTIMER_USEC adjust params for dwm1001:
     CONFIG_ZTIMER_USEC_ADJUST_SET    6
     CONFIG_ZTIMER_USEC_ADJUST_SLEEP  21
 ```
+
+This test application also makes use of the `ztimer_auto_adjust` pseudomodule
+and thereby allows for comparison of the offset values calculated during
+auto-initialization and later during this test.

tests/sys/ztimer_overhead/main.c

@@ -67,9 +67,9 @@ int main(void)
     ZTIMER_USEC->adjust_sleep = 0;
     printf("ZTIMER_USEC auto_adjust params cleared\n");
 
-    printf("zitmer_overhead_set...\n");
+    printf("ztimer_overhead_set...\n");
     ZTIMER_USEC->adjust_set = _ztimer_usec_overhead(SAMPLES, BASE, ztimer_overhead_set);
-    printf("zitmer_overhead_sleep...\n");
+    printf("ztimer_overhead_sleep...\n");
     ZTIMER_USEC->adjust_sleep = _ztimer_usec_overhead(SAMPLES, BASE, ztimer_overhead_sleep);
     printf("ZTIMER_USEC adjust params for %s:\n", RIOT_BOARD);
     printf("    CONFIG_ZTIMER_USEC_ADJUST_SET    %" PRIi16 "\n", ZTIMER_USEC->adjust_set);