pm: cpufreq: boost cpu frequency API support

This patch introduces boost sysfs interface which would enable the
govenor to ack any request for running the system at max freq just before
the system is going to be loaded. The next sample time would be decided
based on the user configured timeout value or the default (0) usec.

To set boost timeout:
echo <in usec> > /sys/devices/system/cpu/cpufreq/interactive/boost_timeout

To enable boost:
echo 1 > /sys/devices/system/cpu/cpu0/cpufreq/boost_cpufreq

Change-Id: I06840c1b27ecef326f48c24d37be452fdf65a001
Signed-off-by: Ruslan Bilovol <ruslan.bilovol@ti.com>
Signed-off-by: David Rodero <david@codiguiel.net>

Conflicts:
	drivers/cpufreq/cpufreq_interactive.c
cpufreq: interactive governor: Delete boost timer on CPUFREQ_GOV_STOP.

Concurrent execution of CPUFREQ_GOV_STOP and interactive_boost_timer()
should be avoided.
Also, interactive_boost() should follow CPUFREQ_GOV_STOP on
flush_work().

Change-Id: I53e897d5ee1834f5cbf0778dd48fc604ec3ea34d
Signed-off-by: Oleg Matcovschi <oleg.matcovschi@ti.com>
Signed-off-by: David Rodero <david@codiguiel.net>

Conflicts:
	drivers/cpufreq/cpufreq_interactive.c