pgsql: Fix CPU-identification macros for RISC-V.

Fix CPU-identification macros for RISC-V.

Turns out that RISC-V intentionally doesn't follow the common
naming pattern for CPU-identification macros. But the point of
2ef57e636 is to have a common pattern, so we're going to override
their opinion.

Discussion: /messages/by-id/CA+hUKGL8Hs-phHPugrWM=5dAkcT897rXyazYzLw-Szxnzgx-rA@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/d3223485546e8579a1703731ef4e39a08a712860

Modified Files
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src/include/c.h | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)