raid6/test/test.c: bug fix: Specify aligned(alignment) attributes to the char arrays

Specifying the aligned attributes to the char data[NDISKS][PAGE_SIZE],
char recovi[PAGE_SIZE] and char recovi[PAGE_SIZE] arrays, so that all
malloc memory is page boundary aligned.

Without these alignment attributes, the test causes a segfault in
userspace when the NDISKS are changed to 4 from 16.

The RAID stripes will be page aligned anyway, so we want to test what
the kernel actually will execute.

Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
Signed-off-by: Gayatri Kammela <gayatri.kammela@intel.com>
Reviewed-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Shaohua Li <shli@fb.com>