Apply #ifdef/#ifndef where possible

Marlin/src/sd/usb_flashdrive/lib-uhs2/settings.h

@@ -153,7 +153,7 @@
 // define XMEM_ACQUIRE_SPI and XMEM_RELEASE_SPI to point to your lock and unlock.
 // NOTE: NO argument is passed. You have to do this within your routine for
 // whatever you are using to lock and unlock.
-#if !defined(XMEM_ACQUIRE_SPI)
+#ifndef XMEM_ACQUIRE_SPI
   #if USE_XMEM_SPI_LOCK || defined(USE_MULTIPLE_APP_API)
     #include <xmem.h>
   #else