drm/i915/hdmi: use generic poll_timeout_us() instead of __wait_for()

Prefer generic poll helpers over i915 custom helpers.

The functional change is losing the exponentially growing sleep of
__wait_for(), which used to be 1, 2, 4, and 8 ms in this particular
case.

Use an arbitrary constant 4 ms sleep instead. The timeout remains,
varying between 20 ms and 3000 ms.

Cc: Suraj Kandpal <[e-mail]>
Reviewed-by: Jouni Högander <[e-mail]>
Link: https://lore.kernel.org/r/fc3[e-mail]
Signed-off-by: Jani Nikula <[e-mail]>

drivers/gpu/drm/i915/display/intel_hdmi.c

···
 #include <linux/delay.h>
 #include <linux/hdmi.h>
 #include <linux/i2c.h>
+#include <linux/iopoll.h>
 #include <linux/slab.h>
 #include <linux/string_helpers.h>
 
···
 	if (timeout < 0)
 		return timeout;
 
-	ret = __wait_for(ret = hdcp2_detect_msg_availability(dig_port,
-							     msg_id, &msg_ready,
-							     &msg_sz),
-			 !ret && msg_ready && msg_sz, timeout * 1000,
-			 1000, 5 * 1000);
+	ret = poll_timeout_us(ret = hdcp2_detect_msg_availability(dig_port, msg_id,
+								  &msg_ready, &msg_sz),
+			      !ret && msg_ready && msg_sz,
+			      4000, timeout * 1000, false);
 	if (ret)
 		drm_dbg_kms(display->drm,
 			    "msg_id: %d, ret: %d, timeout: %d\n",