mtd: denali: fix NAND_CMD_PARAM command

NAND_CMD_PARAM (0xEC) command is not working on the Denali
NAND controller driver.

Unlike NAND_CMD_READID (0x90), when the NAND_CMD_PARAM command
is followed by an address cycle, the target device goes busy.
(R/B# is deasserted)
Wait until the parameter data are ready.

In addition, unnecessary clear_interrupts() should be removed.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Acked-by: Chin Liang See <clsee@altera.com>