drm/tyr: reduce size of doorbell array

Currently the number of doorbells is set to 64 which is an architectural
maximum for the Mali GPU major v10 supported by Tyr. Since each doorbell
needs a 64 KiB page, the doorbell array alone would need 4 MiB of register
memory. Since the doorbell array starts at offset 0x80000, its exclusive
end would be 0x480000, but the rk3588 device that Tyr is compatible with
only provides a 2 MiB iomem region in total.

Reduce the number of doorbells so that they fit into the rk3588 iomem
region. This is consistent with Panthor’s doorbell id assignment.
Doorbell 0 is the global doorbell. Panthor assigns the remaining doorbells
to the active command stream group (CSG) slots. The number of slots is
capped at 16 (MAX_CSG_PRIO + 1). Therefore Panthor uses a maximum of 17
doorbells. The 17 doorbell pages span 0x110000 bytes. Since the doorbell
array starts at offset 0x80000 its exclusive end is 0x190000 and so fits
within the 2 MiB register region.

Signed-off-by: Deborah Brouwer <deborah.brouwer@collabora.com>
Link: https://patch.msgid.link/20260910-b4-doorbell-v1-1-f3ca2f501600@collabora.com
Signed-off-by: Alice Ryhl <aliceryhl@google.com>

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