[sv-ec] Clarification of wildcardbins

Some clarification is needed for creation of wildcardbins.

For the following wildcardbins declaration:

	wildcard bins b[] = { 4'b11??, 4'b1?0? } ;

how many bins are created? My expectation is that this
creates 6 bins for the values 1000, 1001, 1100, 1101, 1110, 1111.

To clarify this, I propose changing the example in
section 18.4.2 as follows:

Replace:
		wildcard bins g12_15 = { 4'b11?? };

	The count of bin g12_15 is incremented when the sampled variable
is between 12 and 15:

		1100 1101 1110 1111


With:
		wildcard bins g[] = { 4'b11??, 4'b1?0? };

	This declaration creates a set of 6 bins, g[8], g[9], g[12],
g[13], g[14], g[15].