Clk sources were not initialized, leading to kernel crash, or possibly to
strange behaviour if DSI was compiled in.
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@nokia.com>

dss_select_clk_source() was rather confusing. Selecting the source with
enums is much clearer.

The clk source selection is also stored into memory, so that we know what
is the selected source, even when clocks are off. This is important during
setup, as we need to what clocks to turn on before the clocks are turned
on.
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@nokia.com>

Loops checking for certain condition were rather inconsistent.
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@nokia.com>
Reported-by: NJuha Leppanen <juha_motorsportcom@luukku.com>

The core files of DSS2. DSS2 commits are split a bit artificially to
make the individual commits smaller, and DSS2 doesn't compile properly
without the rest of the core commits. This shouldn't be a problem, as no
configuration uses DSS2 yet.
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@nokia.com>