opensbi: bump to 1.4

opensbi: bump to 1.4

This release has:
- Synopsys DesignWare APB GPIO driver
- Zicntr and Zihpm support
- Console print improvements
- Smepmp support
- Simple FDT based syscon regmap driver
- Syscon based reboot and poweroff driver
- Non-contiguous hpm counters
- Smcntrpmf support
- Full sparse hartid support
- IPI improvements
- RFENCE improvements
- Zkr support
- Andes custom PMU support
Overall, this release mainly adds more ISA extensions, drivers and other improvements.

https://github.com/riscv-software-src/opensbi/compare/v1.3.1...v1.4

Signed-off-by: Thomas Perrot <thomas.perrot@bootlin.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>