configs: j721e_evm_r5: Disable K3 R5F remoteproc

The J721E R5 SPL will no longer support booting of the Main R5FSS Core0
after the R5 SPL re-architecture for System Firmware split. The MCU R5F
branch-only boot does not use the K3 R5F remoteproc driver, and relies
only on the filesystem (FS) support for now. The K3 R5F remoteproc driver
is therefore no longer needed in R5 SPL, so drop it from the J721E R5
defconfig.

Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Link: https://lore.kernel.org/r/20210726211311.5977-6-s-anna@ti.com