kernel: bump 5.4 to 5.4.51

kernel: bump 5.4 to 5.4.51
update via update_kernel.sh -v -u 5.4

Removed upstreamed patches:
 350-MIPS-Add-missing-EHB-in-mtc0-mfc0-sequence-for-DSPen.patch

Script refreshed patches:
 902-debloat_proc.patch
 904-debloat_dma_buf.patch

Attempted merge conflict in following patches:
 0024-MIPS-lantiq-revert-DSA-switch-driver-PMU-clock-chang.patch

Build system: x86_64
Build tested: ipq806x (Netgear R7800)

Signed-off-by: John Audia <graysky@archlinux.us>
[fixed sha256sum of the tarball]
Signed-off-by: Petr Štetiar <ynezz@true.cz>