RISC-V: KVM: Use find_vma_intersection() to search for intersecting VMAs

RISC-V: KVM: Use find_vma_intersection() to search for intersecting VMAs

There is already a helper function find_vma_intersection() in KVM
for searching intersecting VMAs, use it directly.

Signed-off-by: Quan Zhou <zhouquan@iscas.ac.cn>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/230d6c8c8b8dd83081fcfd8d83a4d17c8245fa2f.1731552790.git.zhouquan@iscas.ac.cn
Signed-off-by: Anup Patel <anup@brainfault.org>