mmc: host: disable only sdhci irqs in sdhci_request

When using the _irqsave variant of spin_lock, irqs are disabled. In the
case of sdhci_request, this can result in relatively long periods of time
in which the irqs are disabled (up to at least 170us observed).
Since in this flow not all interrupts need to be disabled,
we use regular spin_locks here, and disable only sdhci-specific interrupts.
For this, introduce a new sdhci_ops function for enabling/disabling the
platform-specific power irqs.

CRs-Fixed: 709331
Change-Id: Ia9fb0498aab3053b393d677bae097fcd846d8180
Signed-off-by: Lee Susman <lsusman@codeaurora.org>
Signed-off-by: Konstantin Dorfman <kdorfman@codeaurora.org>