Add attribute popup

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/sha256.c b/library/sha256.c
index 4321765..49a233d 100644
--- a/library/sha256.c
+++ b/library/sha256.c
@@ -380,6 +380,11 @@
             SHA256_BLOCK_SIZE) ? 0 : -1;
 }
 
+#if defined(MBEDTLS_POP_TARGET_PRAGMA)
+#pragma clang attribute pop
+#undef MBEDTLS_POP_TARGET_PRAGMA
+#endif
+
 #endif /* MBEDTLS_SHA256_USE_A64_CRYPTO_IF_PRESENT || MBEDTLS_SHA256_USE_A64_CRYPTO_ONLY */