ARM: tegra: add tegra_timer clock

This undoes commit 20f4665 "ARM: tegra: remove tegra_timer from
tegra_list_clks" by bringing back the tegra_timer clock. tegra_timer is
indeed a clock (hidden by the PERIPH_CLK macro) which should be added
to the tegra_list_clks.

The above commit caused tegra_init_timer() failing to get the clk
reference.

Signed-off-by: Sivaram Nair <sivaramn@nvidia.com>
[swarren: added the reverted commit's subject to this patch description]
Signed-off-by: Stephen Warren <swarren@nvidia.com>

arch/arm/mach-tegra/tegra20_clocks_data.c

@@ -953,6 +953,7 @@ PERIPH_CLK(pcie_xclk,	NULL,		  "pcie_xclk",  74,     0,	26000000,  mux_clk_m,
 static struct clk *tegra_list_clks[] = {
 	&tegra_apbdma,
 	&tegra_rtc,
+	&tegra_timer,
 	&tegra_i2s1,
 	&tegra_i2s2,
 	&tegra_spdif_out,

arch/arm/mach-tegra/tegra30_clocks_data.c

@@ -1143,6 +1143,7 @@ struct clk *tegra_list_clks[] = {
 	&tegra_apbdma,
 	&tegra_rtc,
 	&tegra_kbc,
+	&tegra_timer,
 	&tegra_kfuse,
 	&tegra_fuse,
 	&tegra_fuse_burn,