power: smb349: fix possible bug in start/stop_charging

gpio_set_value_cansleep should not be used in a function
that may be called from an interrupt context.

Fix this by using the gpio_set_value() function rather
than the cansleep one in the SMB349 driver.

Change-Id: I6aaa845da8373a3a16ba2f9971fbf9b3a1f22bb4
Signed-off-by: David Keitel <dkeitel@codeaurora.org>