OMAP2+: hwmod: add support for per-class custom device reset functions

OMAP2+: hwmod: add support for per-class custom device reset functions

The standard omap_hwmod.c _reset() code relies on an IP block's
OCP_SYSCONFIG.SOFTRESET register bit to reset the IP block.  This
works for most IP blocks on the chip, but unfortunately not all.  For
example, initiator-only IP blocks often don't have any MPU-accessible
OCP-header registers, and therefore the MPU can't write to any
OCP_SYSCONFIG registers in that block.  Other IP blocks, such as the
IVA and I2C, require a specialized reset sequence.

Since we need to be able to reset these IP blocks as well, allow
custom IP block reset functions to be passed into the hwmod code via a
per-hwmod-class reset function pointer, struct omap_hwmod_class.reset.
If .reset is non-null, then the hwmod _reset() code will call the custom
function instead of the standard OCP SOFTRESET-based code.

As part of this change, rename most of the existing _reset() function
code to _ocp_softreset(), to indicate more clearly that it does not work
for all cases.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Benoît Cousson <b-cousson@ti.com>
Cc: Paul Hunt <hunt@ti.com>
Cc: Stanley Liu <stanley_liu@ti.com>