arc: move linker script in arch/arc/cpu folder

This way we'll be able to use the same one script for either ARC CPU.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>

diff --git a/arch/arc/cpu/arc700/u-boot.lds b/arch/arc/cpu/u-boot.lds
similarity index 100%
rename from arch/arc/cpu/arc700/u-boot.lds
rename to arch/arc/cpu/u-boot.lds