ARM: 7570/1: quiet down the non make -s output

Commit edc88ceb silenced the make -s build, but
inadvertently made louder the non-silent build.  Fix by prepending '@' to each
of the added $(kecho) statements.

Build with edc88ceb:

  CHK     include/generated/compile.h
echo '  Kernel: arch/arm/boot/Image is ready'
  Kernel: arch/arm/boot/Image is ready
  LD      arch/arm/boot/compressed/vmlinux
  OBJCOPY arch/arm/boot/zImage
echo '  Kernel: arch/arm/boot/zImage is ready'
  Kernel: arch/arm/boot/zImage is ready

Build with this fix:
  CHK     include/generated/compile.h
  Kernel: arch/arm/boot/Image is ready
  LD      arch/arm/boot/compressed/vmlinux
  OBJCOPY arch/arm/boot/zImage
  Kernel: arch/arm/boot/zImage is ready

Signed-off-by: Josh Cartwright <josh.cartwright@ni.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>