clang.bbclass: remove mcpu option with qualifiers for the octeontx2 core

[kraj]

Currently, only the '-mcpu=octeontx2' option is removed, and any -mcpu parameters with qualifiers (such as +crc+crypto) are not removed, e.g., '-mcpu=octeontx2+crypto'. Remove these mcpu parameters with qualifiers by using '-mcpu=octeontx2${TUNE_CCARGS_MARCH_OPTS}'.

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