gpio: mb86s7x: Remove superfluous test for ACPI companion

gpio: mb86s7x: Remove superfluous test for ACPI companion

acpi_gpiochip_request_interrupts() will check for ACPI handle of
the GPIO chip parent device and bail out if there is none defined.
Thus, has_acpi_companion() is effectively repeating above and
is not needed in the individual driver.

Assigning ->to_irq() unconditionally doesn't change anything, except
an error code, but this we fix as well by propagating it from
platform_get_irq().

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200512182623.54990-2-andriy.shevchenko@linux.intel.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>