drm/amdgpu/display: use msleep rather than udelay for HDCP

ARM has a 2000us limit for udelay.  Switch to msleep.  This code
executes in a worker thread so shouldn't be an atomic context.
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191217204707.2258744-2-alexander.deucher@amd.com

drivers/gpu/drm/amd/display/modules/hdcp/hdcp2_execution.c

@@ -153,7 +153,7 @@ static enum mod_hdcp_status poll_l_prime_available(struct mod_hdcp *hdcp)
 {
 	enum mod_hdcp_status status;
 	uint8_t size;
-	uint16_t max_wait = 20000; // units of us
+	uint16_t max_wait = 20; // units of ms
 	uint16_t num_polls = 5;
 	uint16_t wait_time = max_wait / num_polls;
 
@@ -161,7 +161,7 @@ static enum mod_hdcp_status poll_l_prime_available(struct mod_hdcp *hdcp)
 		status = MOD_HDCP_STATUS_INVALID_OPERATION;
 	else
 		for (; num_polls; num_polls--) {
-			udelay(wait_time);
+			msleep(wait_time);
 
 			status = mod_hdcp_read_rxstatus(hdcp);
 			if (status != MOD_HDCP_STATUS_SUCCESS)
@@ -474,7 +474,7 @@ static enum mod_hdcp_status locality_check(struct mod_hdcp *hdcp,
 			 hdcp, "lc_init_write"))
 		goto out;
 	if (is_dp_hdcp(hdcp))
-		udelay(16000);
+		msleep(16);
 	else
 		if (!mod_hdcp_execute_and_set(poll_l_prime_available,
 				&input->l_prime_available_poll, &status,