davinci: DA8xx: rename 'psc_ctlr' field into 'gpsc'

Replace badly chosen 'psc_ctlr' name of the 'struct clk' field (PSC already
means "Power and Sleep Controller", so the '_ctlr' postfix makes the name
tautological) with technically correct 'gpsc' (Global PSC -- which contains
all the module registers).

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>