x86emul: MSR indexes are only 32 bits wide

... and hence the respective {read,write}_msr() hook parameter doesn't
need to be "unsigned long".

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -966,7 +966,7 @@ static int hvmemul_write_io_discard(
 }
 
 static int hvmemul_write_msr_discard(
-    unsigned long reg,
+    unsigned int reg,
     uint64_t val,
     struct x86_emulate_ctxt *ctxt)
 {
@@ -1439,7 +1439,7 @@ static int hvmemul_write_cr(
 }
 
 static int hvmemul_read_msr(
-    unsigned long reg,
+    unsigned int reg,
     uint64_t *val,
     struct x86_emulate_ctxt *ctxt)
 {
@@ -1447,7 +1447,7 @@ static int hvmemul_read_msr(
 }
 
 static int hvmemul_write_msr(
-    unsigned long reg,
+    unsigned int reg,
     uint64_t val,
     struct x86_emulate_ctxt *ctxt)
 {
--- a/xen/arch/x86/x86_emulate/x86_emulate.h
+++ b/xen/arch/x86/x86_emulate/x86_emulate.h
@@ -334,7 +334,7 @@ struct x86_emulate_ops
      *  @reg:   [IN ] Register to read.
      */
     int (*read_msr)(
-        unsigned long reg,
+        unsigned int reg,
         uint64_t *val,
         struct x86_emulate_ctxt *ctxt);
 
@@ -343,7 +343,7 @@ struct x86_emulate_ops
      *  @reg:   [IN ] Register to write.
      */
     int (*write_msr)(
-        unsigned long reg,
+        unsigned int reg,
         uint64_t val,
         struct x86_emulate_ctxt *ctxt);