ARM: dts: dra7-evm: Remove pinmux configurations for erratum i869

ARM: dts: dra7-evm: Remove pinmux configurations for erratum i869

Pinmuxing for DRA7x/AM57x family of processors need to be done in IO
isolation as part of initial bootloader executed from SRAM. This is
done as part of iodelay configuration sequence and is required due
to the limitations introduced by erratum ID: i869[1] (IO Glitches
can occur when changing IO settings) and elaborated in the Technical
Reference Manual[2] 18.4.6.1.7 Isolation Requirements.

Only peripheral that is permitted for dynamic pin mux configuration
is MMC and DCAN. MMC is permitted to change to accommodate the
requirements for varied speeds (which require IO-delay support in
kernel as well). DCAN is a result of i893[1] (DCAN initialization
sequence).

DCAN pinmux is retained in this patch. MMC pinmux is missing from
the dra7-evm.dts file and the board is relying on configuration done
by bootloader. A subsequent patch will add MMC pinmux configuration.

A side-effect of this patch is that NAND support is removed. NAND
pins clash with VOUT3 on DRA7-EVM. U-Boot selects VOUT3 over NAND
as per TI EVM application needs.

[1] http://www.ti.com/lit/pdf/sprz429
[2] http://www.ti.com/lit/pdf/sprui30

Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>