arm: at91: Makefile: Compile lowlevel_init only when really necessary

Make sure that lowlevel_init is not compiled when
CONFIG_SKIP_LOWLEVEL_INIT_ONLY is configured.
Signed-off-by: NStefan Roese <sr@denx.de>
Cc: Heiko Schocher <hs@denx.de>
Cc: Andreas Bießmann <andreas@biessmann.org>
Cc: Eugen Hristev <eugen.hristev@microchip.com>
Reviewed-by: NHeiko Schocher <hs@denx.de>
Tested on the taurus board:
Tested-by: NHeiko Schocher <hs@denx.de>

arch/arm/mach-at91/arm926ejs/Makefile

@@ -24,8 +24,10 @@ obj-y	+= timer.o
 endif
 
 ifndef CONFIG_SKIP_LOWLEVEL_INIT
+ifndef CONFIG_SKIP_LOWLEVEL_INIT_ONLY
 obj-y	+= lowlevel_init.o
 endif
+endif
 
 ifdef CONFIG_$(SPL_)SYS_THUMB_BUILD
 ifndef CONFIG_HAS_THUMB2