arm: armv7: solve issue for timer_rate_hz in arch timer

The current value timer_rate_hz causes a problem with function
timer_get_us() from lib time and then an issue with
readx_poll_timeout() function.

With corrected value for tbclk() = timer_rate_hz = CONFIG_SYS_HZ_CLOCK
the weak functions in lib timer can be used:
- get_timer()
- __udelay()
So the specific function in this file are removed.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>

arch/arm/cpu/armv7/arch_timer.c

@@ -17,7 +17,7 @@ int timer_init(void)
 	gd->arch.tbl = 0;
 	gd->arch.tbu = 0;
 
-	gd->arch.timer_rate_hz = CONFIG_SYS_HZ_CLOCK / CONFIG_SYS_HZ;
+	gd->arch.timer_rate_hz = CONFIG_SYS_HZ_CLOCK;
 	return 0;
 }
 
@@ -34,27 +34,9 @@ unsigned long long get_ticks(void)
 }
 
 
-ulong get_timer(ulong base)
-{
-	return lldiv(get_ticks(), gd->arch.timer_rate_hz) - base;
-}
-
 ulong timer_get_boot_us(void)
 {
-	return lldiv(get_ticks(), CONFIG_SYS_HZ_CLOCK / (CONFIG_SYS_HZ * 1000));
-}
-
-void __udelay(unsigned long usec)
-{
-	unsigned long long endtime;
-
-	endtime = lldiv((unsigned long long)usec * gd->arch.timer_rate_hz,
-			1000UL);
-
-	endtime += get_ticks();
-
-	while (get_ticks() < endtime)
-		;
+	return lldiv(get_ticks(), CONFIG_SYS_HZ_CLOCK / 1000000);
 }
 
 ulong get_tbclk(void)