linux-user: Remove unnecessary 'aligned' attribute from TaskState

linux-user: Remove unnecessary 'aligned' attribute from TaskState

The linux-user struct TaskState has an 'aligned(16)' attribute.  When
the struct was first added in commit 851e67a1b46f in 2003, there was
a justification in a comment (still present in the source today):

/* NOTE: we force a big alignment so that the stack stored after is
   aligned too */

because the final field in the struct was "uint8_t stack[0];"
But that field was removed in commit 48e15fc2d in 2010 which
switched us to allocating the stack and the TaskState separately.
Because we allocate the structure with g_new0() rather than as
a local variable, the attribute made no difference to the alignment
of the structure anyway.

Remove the unnecessary attribute, and the corresponding comment.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20220114153732.3767229-2-peter.maydell@linaro.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>