arc: remove redundant GCC version checks

Commit cafa0010 ("Raise the minimum required gcc version to 4.6")
bumped the minimum GCC version to 4.6 for all architectures.

With GCC >= 4.6 assumed, 'upto_gcc44' is empty, 'atleast_gcc44' is y.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>