pkcs7: Support verification of hash with multiple signers

Make `mbedtls_pkcs7_signed_hash_verify` loop over all signatures in the
PKCS7 structure and return success if any of them verify successfully.

Signed-off-by: Nick Child <nick.child@ibm.com>
diff --git a/tests/suites/test_suite_pkcs7.data b/tests/suites/test_suite_pkcs7.data
index daced32..b813c6d 100644
--- a/tests/suites/test_suite_pkcs7.data
+++ b/tests/suites/test_suite_pkcs7.data
@@ -68,4 +68,8 @@
 
 PKCS7 Signed Data Verify with multiple signers #16
 depends_on:MBEDTLS_SHA256_C
-pkcs7_verify_multiple_signers:"data_files/pkcs7_data_multiple_signed.der":"data_files/pkcs7-rsa-sha256-1.crt":"data_files/pkcs7-rsa-sha256-2.crt":"data_files/pkcs7_data.bin"
\ No newline at end of file
+pkcs7_verify_multiple_signers:"data_files/pkcs7_data_multiple_signed.der":"data_files/pkcs7-rsa-sha256-1.crt":"data_files/pkcs7-rsa-sha256-2.crt":"data_files/pkcs7_data.bin"
+
+PKCS7 Signed Data Hash Verify with multiple signers #17
+depends_on:MBEDTLS_SHA256_C
+pkcs7_verify_hash_multiple_signers:"data_files/pkcs7_data_multiple_signed.der":"data_files/pkcs7-rsa-sha256-1.crt":"data_files/pkcs7-rsa-sha256-2.crt":"data_files/pkcs7_data.bin"