selftests/powerpc: Fix: use ucontext_t instead of struct ucontext

[Michael Ellerman]

On Tue, 2018-02-13 at 06:32:55 UTC, Harish wrote:
> With glibc 2.26 'struct ucontext' is removed to improve POSIX
> compliance, which breaks powerpc/alignment_handler selftest.
> Fix the test by using ucontext_t. Tested on ppc, works with older
> glibc versions as well.
> 
> Fixes the following:
> alignment_handler.c: In function ‘sighandler’:
> alignment_handler.c:68:5: error: dereferencing pointer to incomplete type ‘struct ucontext’
>   ucp->uc_mcontext.gp_regs[PT_NIP] += 4;
>      ^~
> 
> Signed-off-by: Harish <harish at linux.vnet.ibm.com>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/ecdf06e1ea5376bba03c155751f686

cheers