Fix cases where exponentiation was not fully tested

In two test cases, the exponentiation computation was not being fully tested
as when A_bytes (the base) == N_bytes (the modulus) -> A = N. When this is the
case A is reduced to 0 and therefore the result of the computation will always
be 0.

This fixes that issue and therefore increases the test coverage to ensure
different computations are actually being run.

Signed-off-by: Chris Jones <christopher.jones@arm.com>
diff --git a/tests/suites/test_suite_mpi.data b/tests/suites/test_suite_mpi.data
index 7a11f5b..0805fa3 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -683,10 +683,10 @@
 mbedtls_mpi_exp_mod:10:"-23":10:"-13":10:"29":10:"":10:"0":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
 
 Test mbedtls_mpi_exp_mod: MAX_SIZE exponent
-mbedtls_mpi_exp_mod_size:2:MBEDTLS_MPI_MAX_SIZE:2:10:"":0
+mbedtls_mpi_exp_mod_size:2:MBEDTLS_MPI_MAX_SIZE:10:10:"":0
 
 Test mbedtls_mpi_exp_mod: MAX_SIZE + 1 exponent
-mbedtls_mpi_exp_mod_size:2:MBEDTLS_MPI_MAX_SIZE + 1:2:10:"":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
+mbedtls_mpi_exp_mod_size:2:MBEDTLS_MPI_MAX_SIZE + 1:10:10:"":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
 
 Test mbedtls_mpi_exp_mod: MAX_SIZE modulus
 mbedtls_mpi_exp_mod_size:2:2:MBEDTLS_MPI_MAX_SIZE:10:"":0