treewide: use full path to counter.h header

The build infrastructure should not be adding the drivers subdirectory
to the include path.  Fix the legacy uses that depended on that
addition.

Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>

drivers/counter/counter_mchp_xec.c

@@ -23,7 +23,7 @@
 #include <logging/log.h>
 LOG_MODULE_REGISTER(counter_mchp_xec, CONFIG_COUNTER_LOG_LEVEL);
 
-#include <counter.h>
+#include <drivers/counter.h>
 #include <soc.h>
 #include <errno.h>
 #include <stdbool.h>

drivers/counter/counter_mcux_gpt.c

@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-#include <counter.h>
+#include <drivers/counter.h>
 #include <fsl_gpt.h>
 #include <logging/log.h>
 

tests/arch/x86/info/src/timer.c

@@ -5,7 +5,7 @@
 
 #include <zephyr.h>
 #include <device.h>
-#include <counter.h>
+#include <drivers/counter.h>
 
 #define NR_SAMPLES 10	/* sample timer 10 times */