[4.14] Backport request: powerpc/perf: Fix IMC_MAX_PMU macro

[Andrew Donnellan]

Dear stable team

Please backport the following patch.

Commit: 7029d1eb0c2c7ee093dc625c679fc277c8eb623b
	("powerpc/perf: Fix IMC_MAX_PMU macro")

Stable tree targeted: 4.14 (applies cleanly)

Justification: This fixes some Oopses observed on boot on one of our 
POWER9 boxes. Fix was identified by bisection, the other patch in the 
2-patch series has already been applied to 4.14 but this one wasn't for 
some reason.

Thanks,
-- 
Andrew Donnellan              OzLabs, ADL Canberra
ajd at linux.ibm.com             IBM Australia Limited