genirq: Use a maple tree for interrupt descriptor management

genirq: Use a maple tree for interrupt descriptor management

The current implementation uses a static bitmap for interrupt descriptor
allocation and a radix tree to pointer store the pointer for lookup.

However, the size of the bitmap is constrained by the build time macro
MAX_SPARSE_IRQS, which may not be sufficient to support high-end servers,
particularly those with GICv4.1 hardware, which require a large interrupt
space to cover LPIs and vSGIs.

Replace the bitmap and the radix tree with a maple tree, which not only
stores pointers for lookup, but also provides a mechanism to find free
ranges. That removes the build time hardcoded upper limit.

Signed-off-by: Shanker Donthineni <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/r/[email protected]