remsim_client: Fix custom ATR '-a' option

So far the option only parsed the hexstring into the atr buffer, but
failed to update the length (from the default value of 2). Also set
atr.len so sending custom ATRs works.

Change-Id: I5deb0a432c05ab0bab5081a2812f6718d4a2ac33
---
M src/client/remsim_client_main.c
1 file changed, 14 insertions(+), 0 deletions(-)

diff --git a/src/client/remsim_client_main.c b/src/client/remsim_client_main.c
index f7f55e7..372cc92 100644
--- a/src/client/remsim_client_main.c
+++ b/src/client/remsim_client_main.c
@@ -117,6 +117,7 @@
 				fprintf(stderr, "ATR malformed\n");
 				exit(2);
 			}
+			cfg->atr.len = rc;
 			break;
 		case 'r':
 			cfg->atr_ignore_rspro = true;

