zephyr: Convert from Zephyr to C99 types

Use C99 types in favor of the Zephyr defined types.

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>
diff --git a/boot/zephyr/arm_cleanup.c b/boot/zephyr/arm_cleanup.c
index 647b8b4..a365926 100644
--- a/boot/zephyr/arm_cleanup.c
+++ b/boot/zephyr/arm_cleanup.c
@@ -12,11 +12,11 @@
 	__disable_irq();
 
 	/* Disable NVIC interrupts */
-	for (u8_t i = 0; i < ARRAY_SIZE(NVIC->ICER); i++) {
+	for (uint8_t i = 0; i < ARRAY_SIZE(NVIC->ICER); i++) {
 		NVIC->ICER[i] = 0xFFFFFFFF;
 	}
 	/* Clear pending NVIC interrupts */
-	for (u8_t i = 0; i < ARRAY_SIZE(NVIC->ICPR); i++) {
+	for (uint8_t i = 0; i < ARRAY_SIZE(NVIC->ICPR); i++) {
 		NVIC->ICPR[i] = 0xFFFFFFFF;
 	}
 }