Possible use of uninitialized value `GHz`

[DYH-Hong]

I tried to build this project using clang++ and it reported some errors different from GCC.

In Line 149, I think we should use MHz, since GHz is not initialized in this branch.

palmtree/CycleTimer.h

Lines 145 to 151 in e4fb5d0

	} else if (MHz_str) {
	*MHz_str = '\0';
	if (1 == sscanf(after_at, "%f", &MHz)) {
	//printf("MHz = %f\n", MHz);
	secondsPerTick_val = 1e-6f / GHz;
	break;
	}

Reference: Line 156

palmtree/CycleTimer.h

Lines 154 to 158 in e4fb5d0

	} else if (1 == sscanf(input, "cpu MHz : %f", &MHz)) {
	//printf("MHz = %f\n", MHz);
	secondsPerTick_val = 1e-6f / MHz;
	break;
	}