arm: reset: Avoid a build error when the reset uclass is enabled

There can be only one do_reset(). When CONFIG_RESET is enabled this is
provided by the reset uclass, and ARM's version should be disabled.

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/arm/lib/Makefile

@@ -47,7 +47,9 @@ obj-y	+= interrupts_64.o
 else
 obj-y	+= interrupts.o
 endif
+ifndef CONFIG_RESET
 obj-y	+= reset.o
+endif
 
 obj-y	+= cache.o
 ifndef CONFIG_ARM64