Add the address alignment to keep the constraint of ARMv7-M architecture same as RAM vector.
ARMv7-M architecture describes the vector table address alignment as following.
The Vector table must be naturally aligned to a power of two
whose alignment value is greater than or equal to (Number of Exceptions supported x 4),
with a minimum alignment of 128 bytes.
I wonder why the implementation of arm_vectors.c does not follow
this constraint of address alignment about ARMv7-M architecture.
Although RAM vector is taken care about it.
I think, as the result it was done by linker script on each board.
At our system, NuttX will be started by bootloader.
To fix the address of entry point(__start) I set the address of entry point to beginning of binary,
so the beginning of binary is not a vector table.
At this case, keeping the address alignment constraint of arm_vectors.c is needed.
072890c1bf