ENGR00225594 mmc: sdhci: remove calling enable clk in interrupt context

ENGR00225594 mmc: sdhci: remove calling enable clk in interrupt context

There's kernel warning without when insmod WiFi module as follows:

------------[ cut here ]------------
WARNING: at kernel/irq/handle.c:130 handle_irq_event_percpu+0x164/0x180()
irq 55 handler sdhci_irq+0x0/0x988 enabled interrupts
Modules linked in: ar6000
[<800471dc>] (unwind_backtrace+0x0/0xfc) from
	[<80072fd0>] (warn_slowpath_common+0x4c/0x64)
[<80072fd0>] (warn_slowpath_common+0x4c/0x64) from
	[<8007307c>] (warn_slowpath_fmt+0x30/0x40)
[<8007307c>] (warn_slowpath_fmt+0x30/0x40) from
	[<800a9f54>] (handle_irq_event_percpu+0x164/0x180)
[<800a9f54>] (handle_irq_event_percpu+0x164/0x180) from
	[<800a9fac>] (handle_irq_event+0x3c/0x5c)
[<800a9fac>] (handle_irq_event+0x3c/0x5c) from
	[<800ac2a8>] (handle_fasteoi_irq+0x98/0x148)
[<800ac2a8>] (handle_fasteoi_irq+0x98/0x148) from
	[<800a9a2c>] (generic_handle_irq+0x2c/0x38)
[<800a9a2c>] (generic_handle_irq+0x2c/0x38) from
	[<80041f60>] (handle_IRQ+0x4c/0xb8)
[<80041f60>] (handle_IRQ+0x4c/0xb8) from
	[<80040f8c>] (__irq_svc+0x4c/0xe8)
[<80040f8c>] (__irq_svc+0x4c/0xe8) from
	[<800420e4>] (default_idle+0x24/0x28)
[<800420e4>] (default_idle+0x24/0x28) from
	[<80042730>] (cpu_idle+0xbc/0xfc)
[<80042730>] (cpu_idle+0xbc/0xfc) from
	[<80008904>] (start_kernel+0x248/0x288)
[<80008904>] (start_kernel+0x248/0x288) from
	[<10008040>] (0x10008040)
---[ end trace 95ab51b95e0e8e5f ]---

it is caused by calling cancel_delayed_work_sync in sdhci_enable_clk, since
it will call spin_unlock_irq which will possibly enable irq in interrupt
context. if sdhci_enable_clk is called in interrupt context this warning
will be shown.

sdhci_enable_clk will be called in interrupt context in the following path:
sdhci_irq->mmc_signal_sdio_irq->mmc_signal_sdio_irq->sdhci_enable_sdio_irq->...
     |____________________interrupt context____________________________________

fix:
Remove calling sdhci_enable_clk in sdhci_enable_sdio_irq. For sdio cards, sdhci
clk will not be disabled, so it is save to remove it.

Signed-off-by: Ryan QIAN <b32804@freescale.com>
Acked-by: Dong Aisheng <b29396@freescale.com>