ARM: decompressor: use better output sections

Place read-only data in a .rodata output section, and the compressed
piggy data in .piggydata.  Place the .got.plt section before the .got
section as is standard ELF practise.

This allows the piggydata to be more easily extracted from the
compressed vmlinux file for verification purposes.

Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
ARM COMPRESS: updates from 3.10.y Google Android.