s390/nmi: use vector instruction macros instead of byte patterns

Use vector instruction macros instead of byte patterns to increase
readability. The generated code is nearly identical:

- 1e8:  e7 0f 10 00 00 36       vlm     %v0,%v15,0(%r1)
- 1ee:  e7 0f 11 00 0c 36       vlm     %v16,%v31,256(%r1)
+ 1e8:  e7 0f 10 00 30 36       vlm     %v0,%v15,0(%r1),3
+ 1ee:  e7 0f 11 00 3c 36       vlm     %v16,%v31,256(%r1),3

By using the VLM macro the alignment hint is automatically specified
too. Even though from a performance perspective it doesn't matter at
all for the machine check code, this shows yet another benefit when
using the macros.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>