ARM: OMAP5: Enable support for AVS0 for OMAP5 production devices

OMAP5432 did go into production with AVS class0 registers which were
mutually exclusive from AVS Class 1.5 registers.

Most OMAP5-uEVM boards use the pre-production Class1.5 which has
production efuse registers set to 0. However on production devices,
these are set to valid data.

scale_vcore logic is already smart enough to detect this and use the
"Nominal voltage" on devices that do not have efuse registers populated.

On a test production device populated as follows:
MPU OPP_NOM:
=> md.l 0x04A0021C4 1
4a0021c4: 03a003e9                               ....
(0x3e9 = 1.01v) vs nom voltage of 1.06v
MPU OPP_HIGH:
=> md.l 0x04A0021C8 1
4a0021c8: 03400485                               ..@.

MM OPP_NOM:
=> md.l 0x04A0021A4 1
4a0021a4: 038003d4                               ....
(0x3d4 = 980mV) vs nom voltage of 1.025v
MM OPP_OD:
=> md.l 0x04A0021A8 1
4a0021a8: 03600403                               ..`.

CORE OPP_NOM:
=> md.l 0x04A0021D8 1
4a0021d8: 000003cf                               ....
(0x3cf = 975mV) vs nom voltage of 1.040v

Since the efuse values are'nt currently used, we do not regress on
existing pre-production samples (they continue to use nominal voltage).

But on boards that do have production samples populated, we can leverage
the optimal voltages necessary for proper operation.

Tested on:
a) 720-2644-001 OMAP5UEVM with production sample.
b) 750-2628-222(A) UEVM5432G-02 with pre-production sample.

Data based on OMAP5432 Technical reference Manual SWPU282AF (May
2012-Revised Aug 2016)

NOTE: All collaterals on OMAP5432 silicon itself seems to have been
removed from ti.com, though EVM details are still available:
http://www.ti.com/tool/OMAP5432-EVM

Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>

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