u-boot-fslc: Avoid restricting parsing for 'imx'

u-boot-fslc: Avoid restricting parsing for 'imx'

The u-boot-fslc does not amend other machines and then cannot be seen
as something that poison other BSP. Adding the restriction to the
common file makes all native tools incompatible.

Fixes:

,----
| [imx23evk] ERROR: Nothing PROVIDES 'u-boot-mxsboot-native'
| [imx23evk] u-boot-fslc-mxsboot-native PROVIDES u-boot-mxsboot-native
|            but was skipped: incompatible with machine imx23evk (not in
|            COMPATIBLE_MACHINE)
`----

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>