net/mlx5: Fix PBMC register mapping

Add reserved mapping to cover all the register in order to avoid setting
arbitrary values to newer FW which implements the reserved fields.

Fixes: 50b4a3c ("net/mlx5: PPTB and PBMC register firmware command support")
Signed-off-by: Aya Levin <ayal@nvidia.com>
Reviewed-by: Moshe Shemesh <moshe@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

include/linux/mlx5/mlx5_ifc.h

@@ -10200,7 +10200,7 @@ struct mlx5_ifc_pbmc_reg_bits {
 
 	struct mlx5_ifc_bufferx_reg_bits buffer[10];
 
-	u8         reserved_at_2e0[0x40];
+	u8         reserved_at_2e0[0x80];
 };
 
 struct mlx5_ifc_qtct_reg_bits {