arch: arm: mach-socfpga: smc: Add dcache flushing and invalidation in smc_send_mailbox()

arch: arm: mach-socfpga: smc: Add dcache flushing and invalidation in smc_send_mailbox()

Adding the dcache flushing and invalidation in the smc_send_mailbox()
At the same time replace the use of u64 with uintptr_t to ensure
compatibility across different architectures and correct the
pointer arithmetic for buffer end address calculation.

Signed-off-by: Mahesh Rao <mahesh.rao@altera.com>
Signed-off-by: Boon Khai Ng <boon.khai.ng@altera.com>
Reviewed-by: Tien Fong Chee <tien.fong.chee@altera.com>
Reviewed-by: Tien Fong Chee <tien.fong.chee@altera.com>