mmc: sdhci-pxav3: fix device wakeup initialization

MMC_PM_KEEP_POWER doesn't imply MMC_PM_WAKE_SDIO_IRQ, we should only
enable device wake up when MMC_PM_WAKE_SDIO_IRQ is set. And "pm_flags"
is the requested pm features, we should not set it in the host driver.

At the same time, device wakeup is disabled by default, so there's no
need to disable device wakeup explicitly.

This patch fixes the warning as following:

[   64.616651] ------------[ cut here ]------------
[   64.616665] WARNING: CPU: 0 PID: 79 at linux/kernel/irq/manage.c:603 irq_set_irq_wake+0xf0/0x11c()
[   64.616667] Unbalanced IRQ 87 wake disable

Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>