configs: stm32mp25: increase SYS_MALLOC_F_LEN to 0x60000

configs: stm32mp25: increase SYS_MALLOC_F_LEN to 0x60000

Due activation of SCMI, we need to increase SYS_MALLOC_F_LEN value
to avoid following message:

U-Boot 2025.04-01224-g75b77a2a6d31-dirty (Apr 25 2025 - 11:23:30 +0200)

alloc space exhausted ptr 400040 limit 400000
alloc space exhausted ptr 400020 limit 400000
alloc space exhausted ptr 400060 limit 400000
alloc space exhausted ptr 400060 limit 400000

Set SYS_MALLOC_F_LEN to 0x60000 to fix this issue.

Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>