arm64: Fix size of __early_cpu_boot_status

__early_cpu_boot_status is of type long. '.long' directive
generates a 32 bit value. Writes to this variable overwrites
32 bits of following adjacent variable and cause corruption.
Use quad assembler directive to allocate 64 bit value.

Change-Id: Ia0953b614ab880302459a279d72b32ce7b016b55
Signed-off-by: Arun KS <arunks@codeaurora.org>