Add PSA interruptible key generation setup & abort APIs

Signed-off-by: Waleed Elmelegy <waleed.elmelegy@arm.com>
diff --git a/tf-psa-crypto/drivers/builtin/include/mbedtls/bignum.h b/tf-psa-crypto/drivers/builtin/include/mbedtls/bignum.h
index 8367cd3..22d5d84 100644
--- a/tf-psa-crypto/drivers/builtin/include/mbedtls/bignum.h
+++ b/tf-psa-crypto/drivers/builtin/include/mbedtls/bignum.h
@@ -238,6 +238,8 @@
 }
 mbedtls_mpi;
 
+#define MBEDTLS_MPI_INIT { 0, 0, 0 }
+
 /**
  * \brief           Initialize an MPI context.
  *