build_helper_configs: Adjusted padding off-set for MUSCA_B1

This patch changes the padding offset used in the hex file
generation for MUSCA_B1 as described below:

0x220000 -> 0xA000000

Change-Id: I4d3c5b84579f4c29158c9db258f126d3f5d149c2
Signed-off-by: Minos Galanakis <minos.galanakis@linaro.org>
1 file changed