base-files: fix nand_upgrade_ubinized()

base-files: fix nand_upgrade_ubinized()

When using "ubiformat" with stdin it requires passing image size using
the -S argument. Provide it just like we do for "ubiupdatevol".

This fixes:
ubiformat: error!: must use '-S' with non-zero value when reading from stdin

This change fixes sysupgrade for bcm53xx and bcm4908 NAND devices
possibly some other targets too.

Cc: Rodrigo Balerdi <lanchon@gmail.com>
Cc: Daniel Golle <daniel@makrotopia.org>
Fixes: 971071212052 ("base-files: accept gzipped nand sysupgrade images")
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Acked-by: Daniel Golle <daniel@makrotopia.org>
Tested-by: Koen Vandeputte <koen.vandeputte@citymesh.com>