mmc: sdhci: Add mmc tracing events for legacy mode.

Add ring buffer tracing events in legacy mode for
debug purpose.
Tracing events include cpu, timestamp, legacy command
opcode, argument, response, interrupts.

Example:
<5> 171912889412: sdhci_prepare_data: mmc0: 0x28=0x0000003c
0x3E=0x00000000
<5> 171912901235: sdhci_set_transfer_mode: mmc0: 0x00=0x00000000
<5> 171912908579: sdhci_send_command: mmc0: updated
0x8=0x00000000 0xC=0x00000013 0xE=0x0000083a
<5> 171912920922: sdhci_irq: mmc0: resp 0: 0x00000900
resp 1: 0x00000000 resp 2: 0x00000000 resp 3: 0x00000000
<5> 171912931339: sdhci_irq: mmc0: intmask: 0x1
<5> 171912938839: sdhci_irq: mmc0: intmask: 0x2
<5> 171912945766: sdhci_finish_data: mmc0: 0x24=0x01f80000

Change-Id: I26d2de3ddf72a74dd84199a9772d48da128796f4
Signed-off-by: Sayali Lokhande <sayalil@codeaurora.org>