TCP Pacing system (HPTS) is missing an API

Recent changes to HPTS have broken an API that was somehow removed (used by user space programs for
time calculations). This commit will add back the inline function that was removed.

Differential Revision:<https://reviews.freebsd.org/D53225>

sys/netinet/tcp_hpts.h

@@ -32,6 +32,10 @@
 #define HPTS_MSEC_IN_SEC 1000
 #define HPTS_USEC_IN_MSEC 1000
 
+/*
+ * The following functions should also be available
+ * to userspace as well.
+ */
 static inline uint32_t
 tcp_tv_to_usec(const struct timeval *sv)
 {
@@ -50,6 +54,13 @@ tcp_tv_to_lusec(const struct timeval *sv)
 	return ((uint64_t)((sv->tv_sec * HPTS_USEC_IN_SEC) + sv->tv_usec));
 }
 
+static inline uint64_t
+tcp_tv_to_lusectick(const struct timeval *sv)
+{
+        return ((uint64_t)((sv->tv_sec * HPTS_USEC_IN_SEC) + sv->tv_usec));
+}
+
+
 struct hpts_diag {
 	uint32_t p_hpts_active; 	/* bbr->flex7 x */
 	uint32_t p_nxt_slot;		/* bbr->flex1 x */