MIPS: VCT: Remove read_spareram reference

The commit ecad289f (OneNAND: Remove
unused read_spareram and add unlock_all as kernel does) forgot to remove
a local reference to read_spareram in board/micronas/vct/ebi_onenand.c,
which causes the following build failure when configured with OneNAND:

ebi_onenand.c: In function 'onenand_board_init':
ebi_onenand.c:196: error: 'struct onenand_chip' has no member named 'read_spareram'
make[1]: *** [ebi_onenand.o] Error 1
make[1]: *** Waiting for unfinished jobs....
make: *** [board/micronas/vct/libvct.a] Error 2

Signed-off-by: Shinya Kuribayashi <skuribay@pobox.com>
Acked-by: Stefan Roese <sr@denx.de>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Scott Wood <scottwood@freescale.com>