srp: Don't use QEMU_PACKED for single elements of a structured type

QEMU_PACKED results in a MinGW compiler warning when it is
used for single structure elements:

warning: 'gcc_struct' attribute ignored

Using QEMU_PACKED for the whole structure avoids the compiler warning
without changing the memory layout.
Signed-off-by: NStefan Weil <sw@weilnetz.de>
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>

hw/srp.h

@@ -177,13 +177,13 @@ struct srp_tsk_mgmt {
     uint8_t    reserved1[6];
     uint64_t   tag;
     uint8_t    reserved2[4];
-    uint64_t   lun QEMU_PACKED;
+    uint64_t   lun;
     uint8_t    reserved3[2];
     uint8_t    tsk_mgmt_func;
     uint8_t    reserved4;
     uint64_t   task_tag;
     uint8_t    reserved5[8];
-};
+} QEMU_PACKED;
 
 /*
  * We need the packed attribute because the SRP spec only aligns the
@@ -198,14 +198,14 @@ struct srp_cmd {
     uint8_t    data_in_desc_cnt;
     uint64_t   tag;
     uint8_t    reserved2[4];
-    uint64_t   lun QEMU_PACKED;
+    uint64_t   lun;
     uint8_t    reserved3;
     uint8_t    task_attr;
     uint8_t    reserved4;
     uint8_t    add_cdb_len;
     uint8_t    cdb[16];
     uint8_t    add_data[0];
-};
+} QEMU_PACKED;
 
 enum {
     SRP_RSP_FLAG_RSPVALID = 1 << 0,