brcmbca: remove CONFIG_BCM_CHIP_ID
Use TARGET_SUBTARGET variable that already contains CHIP_ID
For Kconfig tried fancy solutions like:
default $(shell,echo TARGET_SUBTARGET | tr -d bcm9)
but unfortunately shell is executed in textual substitution phase where TARGET_SUBTARGET is not evaluated.
Related MRs:
refs #12383
Edited by Piotr Kubik