mtd: spi-nor: Remove recently added nor->addr_width == 3 test

mtd: spi-nor: Remove recently added nor->addr_width == 3 test

Remove undocumented nor->addr_width == 3 test. This was added in commit
5d40b3d384dc ("mtd: spi-nor: Add parallel and stacked memories support")
without any explanation in the commit message. Remove it.

This also has a bad side-effect which breaks READ operation of every SPI NOR
which does not use addr_width == 3, e.g. s25fs512s does not work at all. This
is because if addr_width != 3, rem_bank_len is always 0, and if rem_bank_len
is 0, then read_len is 0 and if read_len is 0, then the spi_nor_read() returns
-EIO.

Basic reproducer is as follows:
"
=> sf probe ; sf read 0x50000000 0 0x10000
SF: Detected s25fs512s with page size 256 Bytes, erase size 256 KiB, total 64 MiB
device 0 offset 0x0, size 0x10000
SF: 65536 bytes @ 0x0 Read: ERROR -5
"

Fixes: 5d40b3d384dc ("mtd: spi-nor: Add parallel and stacked memories support")
Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>