sim: fix gcc 4.9.2 + -std=gnu11 error

Remove "(const struct osim_card_sw)" infront of OSIM_CARD_SW_LAST, so
debian 8's gcc 4.9.2 doesn't fail anymore with the following error each
time the macro is used:
	card_fs_sim.c:105:1: error: initializer element is not constant

I verified with docker that there aren't any other build errors with gcc
4.9.2.

Fixes: OS#4991
Change-Id: I9d3abbf9812dc09201eff0e9f7542cddedb6848b
diff --git a/include/osmocom/sim/sim.h b/include/osmocom/sim/sim.h
index bfd1ac9..72e7904 100644
--- a/include/osmocom/sim/sim.h
+++ b/include/osmocom/sim/sim.h
@@ -283,7 +283,7 @@
 	} u;
 };
 
-#define OSIM_CARD_SW_LAST	(const struct osim_card_sw) {	\
+#define OSIM_CARD_SW_LAST	{			\
 	.code = 0, .mask = 0, .type = SW_TYPE_NONE,	\
 	.class = SW_CLS_NONE, .u.str = NULL		\
 }