mtd: spi-nor: Clear Winbond SR3 WPS bit on boot

mtd: spi-nor: Clear Winbond SR3 WPS bit on boot

Some Winbond SPI NORs have special SR3 register which is
used among other things to control whether non-standard
"Individual Block/Sector Write Protection" (WPS bit)
locking scheme is activated. This non-standard locking
scheme is not supported by either U-Boot or Linux SPI
NOR stack so make sure it is disabled, otherwise the
SPI NOR may appear locked for no obvious reason.

This SR3 WPS appears e.g. on W25Q16FW which has the same ID as
W25Q16DW, but the W25Q16DW does not implement the SR3 WPS bit.

Signed-off-by: Marek Vasut <marex@denx.de>