mtd: spi-nor: macronix: Add SECT_4K to mx25l12805d

According to the mx25l12805d datasheet it supports using 4K or 64K sectors.
So lets add the SECT_4K to enable 4K sector usage.

Datasheet: https://www.mxic.com.tw/Lists/Datasheet/Attachments/7321/MX25L12805D,%203V,%20128Mb,%20v1.2.pdf



Cc: Luka Perkov <luka.perkov@sartura.hr>
Signed-off-by: Robert Marko <robert.marko@sartura.hr>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Link: https://lore.kernel.org/r/20200915100623.708736-1-robert.marko@sartura.hr