qemu: remove broken patch

The necessary patch has been imported into musl so no need
to cast the sigevent struct to a more glibc-like one.

srcpkgs/qemu/patches/musl-fix-sigevent-and-sigval_t.patch

@@ -1,27 +0,0 @@
-Note: Remove this patch with musl 1.2.2
-
---- a/linux-user/syscall.c
-+++ b/linux-user/syscall.c
-@@ -5020,10 +5020,21 @@
- #ifndef HAVE_SIGEV_NOTIFY_THREAD_ID
- #define sigev_notify_thread_id _sigev_un._tid
- #endif
- 
--static inline abi_long target_to_host_sigevent(struct sigevent *host_sevp,
-+struct host_sigevent {
-+    union sigval sigev_value;
-+    int sigev_signo;
-+    int sigev_notify;
-+    union {
-+       char _pad[64 - sizeof(int) * 2 - sizeof(union sigval)];
-+       int _tid;
-+    } _sigev_un;
-+};
-+
-+static inline abi_long target_to_host_sigevent(struct sigevent *sevp,
-                                                abi_ulong target_addr)
- {
-+    struct host_sigevent *host_sevp = (struct host_sigevent *) sevp;
-     struct target_sigevent *target_sevp;
- 
-     if (!lock_user_struct(VERIFY_READ, target_sevp, target_addr, 1)) {