target/ppc: Change MSR_* to follow POWER ISA numbering convention

target/ppc: Change MSR_* to follow POWER ISA numbering convention

Today we have the issue where MSR_* values are the 'inverted order'
bit numbers from what the ISA specifies. e.g. MSR_LE is bit 63 but
is defined as 0 in QEMU.

Add a macro to be used to convert from QEMU order to ISA order.

This solution requires less changes than to use the already defined
PPC_BIT macro, which would turn MSR_* in masks instead of the numbers
itself.

Signed-off-by: Víctor Colombo <victor.colombo@eldorado.org.br>
Acked-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220504210541.115256-23-victor.colombo@eldorado.org.br>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>