riscv: Use kcalloc() instead of kzalloc()

As noted in the "Deprecated Interfaces, Language Features, Attributes,
and Conventions" documentation [1], size calculations (especially
multiplication) should not be performed in memory allocator (or similar)
function arguments due to the risk of them overflowing. This could lead
to values wrapping around and a smaller allocation being made than the
caller was expecting. Using those allocations could lead to linear
overflows of heap memory and other misbehaviors.

So, use the purpose specific kcalloc() function instead of the argument
count * size in the kzalloc() function.

Also, it is preferred to use sizeof(*pointer) instead of sizeof(type)
due to the type of the variable can change and one needs not change the
former (unlike the latter).

Link: https://www.kernel.org/doc/html/next/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [1]
Link: https://github.com/KSPP/linux/issues/162Signed-off-by: Erick Archer <erick.archer@gmx.com>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20240120135400.4710-1-erick.archer@gmx.comSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/kernel/unaligned_access_speed.c

@@ -218,8 +218,7 @@ static int check_unaligned_access_speed_all_cpus(void)
 {
 	unsigned int cpu;
 	unsigned int cpu_count = num_possible_cpus();
-	struct page **bufs = kzalloc(cpu_count * sizeof(struct page *),
-				     GFP_KERNEL);
+	struct page **bufs = kcalloc(cpu_count, sizeof(*bufs), GFP_KERNEL);
 
 	if (!bufs) {
 		pr_warn("Allocation failure, not measuring misaligned performance\n");