pinctrl: single: Fix probe failure getting register area size

If reg property of pinctrl-single node requires address translation then
probe fails with following message:

single-pinctrl pinctrl@4301c000: failed to get base register size

This is because driver uses dev_read_addr_size() to get size which also
tries to fetch untranslated addr and fails.
Fix this by using dev_read_addr_size_index() which takes care of address
translation and also makes following dev_read_addr() call redundant.

This fixes Ethernet failures on TI's AM654 based EVMs due to lack of
pinmux configuration.

Fixes: 9fd8a430 ("pinctrl: single: get register area size by device API")
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>