mlx4: fix "initializer element not constant" compiler error

A recent commit e8937681 ("devlink: prepare to support region
operations") used the region_cr_space_str and region_fw_health_str
variables as initializers for the devlink_region_ops structures.

This can result in compiler errors:
drivers/net/ethernet/mellanox//mlx4/crdump.c:45:10: error: initializer
element is not constant
   .name = region_cr_space_str,
           ^
drivers/net/ethernet/mellanox//mlx4/crdump.c:45:10: note: (near
initialization for ‘region_cr_space_ops.name’)
drivers/net/ethernet/mellanox//mlx4/crdump.c:50:10: error: initializer
element is not constant
   .name = region_fw_health_str,

The variables were made to be "const char * const", indicating that both
the pointer and data were constant. This was enough to resolve this on
recent GCC (gcc (GCC) 9.2.1 20190827 (Red Hat 9.2.1-1) for this author).

Unfortunately this is not enough for older compilers to realize that the
variable can be treated as a constant expression.

Fix this by introducing macros for the string and use those instead of
the variable name in the region ops structures.
Reported-by: tanhuazhong <tanhuazhong@huawei.com>
Fixes: e8937681 ("devlink: prepare to support region operations")
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx4/crdump.c

@@ -38,16 +38,19 @@
 #define CR_ENABLE_BIT_OFFSET		0xF3F04
 #define MAX_NUM_OF_DUMPS_TO_STORE	(8)
 
-static const char * const region_cr_space_str = "cr-space";
-static const char * const region_fw_health_str = "fw-health";
+#define REGION_CR_SPACE "cr-space"
+#define REGION_FW_HEALTH "fw-health"
+
+static const char * const region_cr_space_str = REGION_CR_SPACE;
+static const char * const region_fw_health_str = REGION_FW_HEALTH;
 
 static const struct devlink_region_ops region_cr_space_ops = {
-	.name = region_cr_space_str,
+	.name = REGION_CR_SPACE,
 	.destructor = &kvfree,
 };
 
 static const struct devlink_region_ops region_fw_health_ops = {
-	.name = region_fw_health_str,
+	.name = REGION_FW_HEALTH,
 	.destructor = &kvfree,
 };