net: broadcom: fix a mistake about ioremap resource

net: broadcom: fix a mistake about ioremap resource

Commit d7a5502b0bb8b ("net: broadcom: convert to
devm_platform_ioremap_resource_byname()") will broke this driver.
idm_base and nicpm_base were optional, after this change, they are
mandatory. it will probe fails with -22 when the dtb doesn't have them
defined. so revert part of this commit and make idm_base and nicpm_base
as optional.

Fixes: d7a5502b0bb8bde ("net: broadcom: convert to devm_platform_ioremap_resource_byname()")
Reported-by: Jonathan Richardson <[email protected]>
Cc: Scott Branden <[email protected]>
Cc: Ray Jui <[email protected]>
Cc: Florian Fainelli <[email protected]>
Cc: David S. Miller <[email protected]>
Signed-off-by: Dejin Zheng <[email protected]>
Acked-by: Florian Fainelli <[email protected]>
Signed-off-by: David S. Miller <[email protected]>