valgrind: Update to version 3.26.0

valgrind: Update to version 3.26.0

The following patches were removed:
 * 010-486180-Valgrind-MIPS-VexGuestArchState-has-no-member.patch [1]
 * 020-mips-skip-using-shared-syscall-numbers-for-mips32.patch [2]
 * 021-mips-skip-using-shared-syscall-numbers-for-mips64.patch [3]

The License changed from GPLv2 to GPLv3. [4]

RISCV64/Linux is supporterd since version 3.25.0.

[1]: https://sourceware.org/git/?p=valgrind.git;a=commitdiff;h=7214886886bce9029f325214156c02dcfff760d5
[2]: https://sourceware.org/git/?p=valgrind.git;a=commitdiff;h=54d6ad3348fb50f5b972fe9c05d0d8757bfe73ba
[3]: https://sourceware.org/git/?p=valgrind.git;a=commitdiff;h=efaa17e53a750d5f0f4c138b507b1b104729ed67
[4]: https://sourceware.org/git/?p=valgrind.git;a=commitdiff;h=3392155359822c0d4e8bb371862e92425054d02a

Link: https://github.com/openwrt/openwrt/pull/20537
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>