sh: Remove compressed kernel libgcc dependency.

SH-2A is unable to combine the kernel and libgcc objects due to
fundamental disagreements over FDPIC settings. As the kernel already
contains all of the libgcc bits broken out, there's not much need to
bother with the linking anymore, as everything can already be derived
from the lib dir.

This simply plugs in the necessary bits to ensure that everything is
built uniformly, enabling us to wean the compressed build off of explicit
libgcc linking.

Reported-by: Phil Edworthy <phil.edworthy@renesas.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>