soc/amd/*/bootblock,early_fch: rework i2c_scl_pins configuration

drive_scl in soc/amd/common/block/i2c/i2c.c writes the raw GPIO MMIO
configuration register and drives it as output, so don't initially
configure the GPIO as input with no pull up/down. This is a preparation
to use the common AMD GPIO access functions instead of the raw register
accesses, since the gpio_set function only sets the output value, but
doesn't reconfigure the direction. Using gpio_output there instead would
reconfigure the direction as well, but would result in doubling the
number of MMIO accesses, so just configure the GPIOs correctly right
away to avoid that.

TEST=The waveform on the SCL pin of I2C3 on a barla/careena Chromebook
looks exactly the same as before during the reset_i2c_peripherals call.
This was probed at the SCL pad of the unpopulated I2C level shifter on
the side that is connected to the SoC.

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Change-Id: I8e94afe0c755a02abcc722d5094e220d8781f8f5
Reviewed-on: https://review.coreboot.org/c/coreboot/+/56807
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

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