vboot: remove trailing newline from sysfs

Upstream chromeos_acpi driver[1] appends a newline at the end of return
string while downstream chromeos_acpi driver[2] doesn't append newlines.

To make it ready to switch to upstream chromeos_acpi driver, remove the
trailing newline from sysfs if any.

[1]: https://elixir.bootlin.com/linux/v6.4/source/drivers/platform/chrome/chromeos_acpi.c#L91
[2]: https://crrev.com/aa20555b4f829ecc8f8e7c936e3979ad89285f75/drivers/platform/x86/chromeos_acpi.c#528

BRANCH=none
BUG=b:291036452
TEST=crossystem fwid

Change-Id: I4060fa73c42c30c142a4c024d6624144c84c317c
Signed-off-by: Tzung-Bi Shih <tzungbi@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/4719309
Reviewed-by: Yu-Ping Wu <yupingso@chromium.org>
2 files changed