perf: Fix typos in sample code in the perf_event.h header

	/*

	 * Bits needed to read the hw events in user-space.

	 *

	 *   u32 seq, time_mult, time_shift, idx, width;

	 *   u32 seq, time_mult, time_shift, index, width;

	 *   u64 count, enabled, running;

	 *   u64 cyc, time_offset;

	 *   s64 pmc = 0;

	 *       time_shift  = pc->time_shift;

	 *     }

	 *

	 *     idx = pc->index;

	 *     index = pc->index;

	 *     count = pc->offset;

	 *     if (pc->cap_usr_rdpmc && idx) {

	 *     if (pc->cap_user_rdpmc && index) {

	 *       width = pc->pmc_width;

	 *       pmc = rdpmc(idx - 1);

	 *       pmc = rdpmc(index - 1);

	 *     }

	 *

	 *     barrier();

	};

	/*

	 * If cap_usr_rdpmc this field provides the bit-width of the value

	 * If cap_user_rdpmc this field provides the bit-width of the value

	 * read using the rdpmc() or equivalent instruction. This can be used

	 * to sign extend the result like:

	 *

	 *

	 * Where time_offset,time_mult,time_shift and cyc are read in the

	 * seqcount loop described above. This delta can then be added to

	 * enabled and possible running (if idx), improving the scaling:

	 * enabled and possible running (if index), improving the scaling:

	 *

	 *   enabled += delta;

	 *   if (idx)

	 *   if (index)

	 *     running += delta;

	 *

	 *   quot = count / running;