spl: nand: simple: replace readb() with chip specific read_buf()

spl: nand: simple: replace readb() with chip specific read_buf()

Some NAND controllers define custom functions to read data out,
respect this in order to correctly support bad block handling in
simple SPL NAND framework.

NAND controller specific read_buf() is used even to read 1 byte in
case of connected 8-bit NAND device, it turns out that read_byte()
may become outdated.

Signed-off-by: Vladimir Zapolskiy <[email protected]>
Cc: Tom Rini <[email protected]>
Cc: Tom Warren <[email protected]>
Acked-by: Scott Wood <[email protected]>