kexec: allocate the kexec control page with KEXEC_CONTROL_MEMORY_GFP

kexec: allocate the kexec control page with KEXEC_CONTROL_MEMORY_GFP

[ Upstream commit 7e01b5acd88b3f3108d8c4ce44e3205d67437202 ]

Introduce KEXEC_CONTROL_MEMORY_GFP to allow the architecture code
to override the gfp flags of the allocation for the kexec control
page. The loop in kimage_alloc_normal_control_pages allocates pages
with GFP_KERNEL until a page is found that happens to have an
address smaller than the KEXEC_CONTROL_MEMORY_LIMIT. On systems
with a large memory size but a small KEXEC_CONTROL_MEMORY_LIMIT
the loop will keep allocating memory until the oom killer steps in.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>