hwmon: (gpd-fan) Fix compilation error in non-ACPI builds

Building gpd-fan driver without CONFIG_ACPI results in the following
build errors:

drivers/hwmon/gpd-fan.c: In function ‘gpd_ecram_read’:
drivers/hwmon/gpd-fan.c:228:9: error: implicit declaration of function ‘outb’ [-Werror=implicit-function-declaration]
228 | outb(0x2E, addr_port);
| ^~~~
drivers/hwmon/gpd-fan.c:241:16: error: implicit declaration of function ‘inb’ [-Werror=implicit-function-declaration]
241 | *val = inb(data_port);

The definitions for inb() and outb() come from <linux/io.h>
(specifically through <asm/io.h>), which is implicitly included via
<acpi_io.h>. When CONFIG_ACPI is not set, <acpi_io.h> is not included
resulting in <linux/io.h> to be omitted as well.

Since the driver does not depend on ACPI, remove <linux/acpi.h> and add
<linux/io.h> directly to fix the compilation errors.

Signed-off-by: Gopi Krishna Menon <krishnagopi487@gmail.com>
Link: https://lore.kernel.org/r/20251024202042.752160-1-krishnagopi487@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>