platform/mellanox: mlxbf-pmc: Fix an IS_ERR() vs NULL bug in mlxbf_pmc_map_counters

The devm_ioremap() function returns NULL on error, it doesn't return
error pointers. Also according to doc of device_property_read_u64_array,
values in info array are properties of device or NULL.

Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Link: https://lore.kernel.org/r/20211210070753.10761-1-linmq006@gmail.com


Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>