ARM: tegra: ensure nvtboot_boot_x0 alignment

nvtboot_boot_x0 is a 64-bit variable and hence must be 64-bit aligned.
So far this has happened by accident! Fix the code so this is guaranteed.

This fixes the following build error:
... relocation truncated to fit: R_AARCH64_LDST64_ABS_LO12_NC
    against symbol `nvtboot_boot_x0' ...

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>

arch/arm/mach-tegra/tegra186/nvtboot_ll.S

@@ -9,6 +9,7 @@
 #include <config.h>
 #include <linux/linkage.h>
 
+.align 8
 .globl	nvtboot_boot_x0
 nvtboot_boot_x0:
 	.dword 0