lib/vdso: Mark do_hres() and do_coarse() as __always_inline

Performance numbers for Intel(R) Core(TM) i5-6300U CPU @ 2.40GHz
(more clock_gettime() cycles - the better):

clock            | before     | after      | diff
----------------------------------------------------------
monotonic        |  153222105 |  166775025 | 8.8%
monotonic-coarse |  671557054 |  691513017 | 3.0%
monotonic-raw    |  147116067 |  161057395 | 9.5%
boottime         |  153446224 |  166962668 | 9.1%

The improvement for arm64 for monotonic and boottime is around 3.5%.

clock            | before     | after      | diff
==================================================
monotonic          17326692     17951770     3.6%
monotonic-coarse   43624027     44215292     1.3%
monotonic-raw      17541809     17554932     0.1%
boottime           17334982     17954361     3.5%

[ tglx: Avoid the goto ]
Signed-off-by: Andrei Vagin <avagin@gmail.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20191112012724.250792-3-dima@arista.com

lib/vdso/gettimeofday.c

@@ -38,7 +38,7 @@ u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult)
 }
 #endif
 
-static int do_hres(const struct vdso_data *vd, clockid_t clk,
+static __always_inline int do_hres(const struct vdso_data *vd, clockid_t clk,
 		   struct __kernel_timespec *ts)
 {
 	const struct vdso_timestamp *vdso_ts = &vd->basetime[clk];
@@ -68,8 +68,8 @@ static int do_hres(const struct vdso_data *vd, clockid_t clk,
 	return 0;
 }
 
-static int do_coarse(const struct vdso_data *vd, clockid_t clk,
-		      struct __kernel_timespec *ts)
+static __always_inline int do_coarse(const struct vdso_data *vd, clockid_t clk,
+				     struct __kernel_timespec *ts)
 {
 	const struct vdso_timestamp *vdso_ts = &vd->basetime[clk];
 	u32 seq;
@@ -99,13 +99,15 @@ __cvdso_clock_gettime_common(clockid_t clock, struct __kernel_timespec *ts)
 	 */
 	msk = 1U << clock;
 	if (likely(msk & VDSO_HRES))
-		return do_hres(&vd[CS_HRES_COARSE], clock, ts);
+		vd = &vd[CS_HRES_COARSE];
 	else if (msk & VDSO_COARSE)
 		return do_coarse(&vd[CS_HRES_COARSE], clock, ts);
 	else if (msk & VDSO_RAW)
-		return do_hres(&vd[CS_RAW], clock, ts);
+		vd = &vd[CS_RAW];
+	else
+		return -1;
 
-	return -1;
+	return do_hres(vd, clock, ts);
 }
 
 static __maybe_unused int