zephyr: Clean up motion_sensor header
zephyr: Clean up motion_sensor header

Remove motion_sensors_alt[] from the motion_sense header,
because the array should be used only in motionsense_sensors file.

BUG=b:183990188
BRANCH=none
TEST=zmake testall

Signed-off-by: Dawid Niedzwiecki <73bc8c219b84b29e82d4338ec2e55b540c845bc6@semihalf.com>
Change-Id: I0b0e87c72d48a2b27b684612c7a752fa487c4810
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2939670
Reviewed-by: Yuval Peress <50dc11c009bd4d7e9d9d15a383c1743ce5ee82ef@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec