pinctrl: renesas: checker: Fix miscalculation of number of states

The checker failed to validate all enum IDs in the description of a
register with fixed-width register fields, due to a miscalculation of
the number of described states: each register field of n bits can have
"1 << n" possible states, not "1".

Increase SH_PFC_MAX_ENUMS accordingly, now more enum IDs are checked
(SH-Mobile AG5 has more than 4000 enum IDs defined).

Fixes: 12d057ba ("pinctrl: sh-pfc: checker: Add check for enum ID conflicts")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/6d8a6a05564f38f9d20464c1c17f96e52740cf6a.1645460429.git.geert+renesas@glider.be