u-boot: remove sourceipk workaround
u-boot: remove sourceipk workaround

* The sourceipk has been enhancedto tell the packaging to ignore the
  sourceipk files when stripping and debug splitting.

Signed-off-by: Jacob Stiffler <0ec61db87821c27ca8ee6f3e24c6f93fdbb785d4@ti.com>

rcn-ee/meta-processor-sdk,rcn-ee/meta-processor-sdk,rcn-ee/meta-processor-sdk