mfd: stmpe: add pull up/down register offsets for STMPE

This adds the register offsets for pull up/down for the STMPE
1601, 1801 and 24xx expanders. This is used to bias GPIO lines
and keypad lines.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>