Replace __ASSEMBLY__ with compiler-builtin __ASSEMBLER__

NOTE: __ASSEMBLY__ macro is now deprecated in favor of __ASSEMBLER__.

All common C compilers predefine a macro called __ASSEMBLER__ when
preprocessing a .S file. There is no reason for TF-A to define it's own
__ASSEMBLY__ macro for this purpose instead. To unify code with the
export headers (which use __ASSEMBLER__ to avoid one extra dependency),
let's deprecate __ASSEMBLY__ and switch the code base over to the
predefined standard.

Change-Id: Id7d0ec8cf330195da80499c68562b65cb5ab7417
Signed-off-by: Julius Werner <jwerner@chromium.org>
diff --git a/include/drivers/st/stm32_gpio.h b/include/drivers/st/stm32_gpio.h
index 4320eaf..e241f58 100644
--- a/include/drivers/st/stm32_gpio.h
+++ b/include/drivers/st/stm32_gpio.h
@@ -45,13 +45,13 @@
 #define GPIO_PULL_DOWN		0x02
 #define GPIO_PULL_MASK		U(0x03)
 
-#ifndef __ASSEMBLY__
+#ifndef __ASSEMBLER__
 #include <stdint.h>
 
 int dt_set_pinctrl_config(int node);
 void set_gpio(uint32_t bank, uint32_t pin, uint32_t mode, uint32_t speed,
 	      uint32_t pull, uint32_t alternate, uint8_t status);
 void set_gpio_secure_cfg(uint32_t bank, uint32_t pin, bool secure);
-#endif /*__ASSEMBLY__*/
+#endif /*__ASSEMBLER__*/
 
 #endif /* STM32_GPIO_H */