drm_hwcomposer: Use __ANDROID_API__ instead of PLATFORM_SDK_VERSION

__ANDROID_API__ definition is available by default in AOSP and NDK.

It also exported by standard system clang when the user sets
the '-target <ARCH>-linux-android<LEVEL>' compiler flag.

Reason for this change is integration of meson build script, where
otherwise the user has to provide the API level manually.

Signed-off-by: Roman Stratiienko <r.stratiienko@gmail.com>
diff --git a/hwc2_device/HwcDisplay.h b/hwc2_device/HwcDisplay.h
index 40c90a3..0334470 100644
--- a/hwc2_device/HwcDisplay.h
+++ b/hwc2_device/HwcDisplay.h
@@ -68,12 +68,12 @@
                                  uint32_t *num_elements, hwc2_layer_t *layers,
                                  int32_t *layer_requests);
   HWC2::Error GetDisplayType(int32_t *type);
-#if PLATFORM_SDK_VERSION > 27
+#if __ANDROID_API__ > 27
   HWC2::Error GetRenderIntents(int32_t mode, uint32_t *outNumIntents,
                                int32_t *outIntents);
   HWC2::Error SetColorModeWithIntent(int32_t mode, int32_t intent);
 #endif
-#if PLATFORM_SDK_VERSION > 28
+#if __ANDROID_API__ > 28
   HWC2::Error GetDisplayIdentificationData(uint8_t *outPort,
                                            uint32_t *outDataSize,
                                            uint8_t *outData);
@@ -82,7 +82,7 @@
   HWC2::Error GetDisplayBrightnessSupport(bool *supported);
   HWC2::Error SetDisplayBrightness(float);
 #endif
-#if PLATFORM_SDK_VERSION > 29
+#if __ANDROID_API__ > 29
   HWC2::Error GetDisplayConnectionType(uint32_t *outType);
 
   HWC2::Error SetActiveConfigWithConstraints(