hw/xen: Remove unnecessary xen_hvm_inject_msi() stub

Since commit 04b0de0ee8 ("xen: factor out common functions")
xen_hvm_inject_msi() stub is not required.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Message-Id: <20231114143816.71079-8-philmd@linaro.org>
diff --git a/stubs/xen-hw-stub.c b/stubs/xen-hw-stub.c
index 7d7ffe8..6cf0e9a 100644
--- a/stubs/xen-hw-stub.c
+++ b/stubs/xen-hw-stub.c
@@ -24,10 +24,6 @@
     return -1;
 }
 
-void xen_hvm_inject_msi(uint64_t addr, uint32_t data)
-{
-}
-
 int xen_is_pirq_msi(uint32_t msi_data)
 {
     return 0;