extcon: axp288: Convert to using managed resources

Use resource managed functions devm_usb_get_phy and
devm_gpio_request to make error path simpler. To be
compatible the change, various gotos are replaced
with direct returns and unnecessary label
gpio_req_failed is dropped.

Also, remove function axp288_extcon_remove as it is
now redundant.

Signed-off-by: Vaishali Thakkar <vthakkar1994@gmail.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>