init: support longer command lines

The Linux kernel supports command lines up to 2048 bytes on x86,
see COMMAND_LINE_SIZE in asm/setup.h.

If any androidboot.xxxx arguments were past the 1024 byte limit
here, they were lost.

Change-Id: I6247c511a7de04109490fffa0125801d274a5501
Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>