selftests: memory-hotplug: add required configs

add CONFIG_MEMORY_HOTREMOVE=y in config
without this config, /sys/devices/system/memory/memory*/removable
always return 0, I endup getting an early skip during test
Signed-off-by: Lei Yang <Lei.Yang@windriver.com>
Signed-off-by: Shuah Khan (Samsung OSG) <shuah@kernel.org>

tools/testing/selftests/memory-hotplug/config

@@ -2,3 +2,4 @@ CONFIG_MEMORY_HOTPLUG=y
 CONFIG_MEMORY_HOTPLUG_SPARSE=y
 CONFIG_NOTIFIER_ERROR_INJECTION=y
 CONFIG_MEMORY_NOTIFIER_ERROR_INJECT=m
+CONFIG_MEMORY_HOTREMOVE=y