Use 4k sectors when accessing the U-Boot environment on the 64MiB
SPI-NOR flash chip found in the UniFi 6 LR. The speeds up environment
write access as only 4kB instead of 64kB have to be written.
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
(cherry picked from commit f0adf253fdcf78ce005dad9652b405a4ad2726e6)
aebb19d34b