ARM: 9189/1: decompressor: fix unneeded rebuilds of library objects

Since commit 251cc826 ("ARM: 9154/1: decompressor: do not copy source
files while building"), the following three are rebuilt every time.

  AS      arch/arm/boot/compressed/lib1funcs.o
  AS      arch/arm/boot/compressed/ashldi3.o
  AS      arch/arm/boot/compressed/bswapsdi2.o

Move the "OBJS += ..." line up so these objects are added to 'targets'.

Fixes: 251cc826 ("ARM: 9154/1: decompressor: do not copy source files while building")
Reported-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>