target/ppc: Merge fsqrt and fsqrts helpers

target/ppc: Merge fsqrt and fsqrts helpers

These two helpers are almost identical, differing only by the softfloat
operation it calls. Merge them into one using a macro.
Also, take this opportunity to capitalize the helper name as we moved
the instruction to decodetree in a previous patch.

Signed-off-by: Víctor Colombo <victor.colombo@eldorado.org.br>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220905123746.54659-4-victor.colombo@eldorado.org.br>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>