s390/crash: use the correct type for memory allocation

get_elfcorehdr_size() returns a size_t, so there is no real point to
store it in a u32.

Turn 'alloc_size' into a size_t.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/0756118c9058338f3040edb91971d0bfd100027b.1686688212.git.christophe.jaillet@wanadoo.frSigned-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

arch/s390/kernel/crash_dump.c

@@ -568,9 +568,9 @@ static size_t get_elfcorehdr_size(int mem_chunk_cnt)
 int elfcorehdr_alloc(unsigned long long *addr, unsigned long long *size)
 {
 	Elf64_Phdr *phdr_notes, *phdr_loads;
+	size_t alloc_size;
 	int mem_chunk_cnt;
 	void *ptr, *hdr;
-	u32 alloc_size;
 	u64 hdr_off;
 
 	/* If we are not in kdump or zfcp/nvme dump mode return */