target/arm: Clean up of register field definitions

target/arm: Clean up of register field definitions

Clean up the definitions of NSW and NSA fields in the VTCR register.
These two fields are already defined properly using FIELD() so they are
actually duplications. Also, define the NSW and NSA fields in the
VSTCR register using FIELD() and remove their definitions based on VTCR
fields.

Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org>
Message-id: 20250725014755.2122579-1-gustavo.romero@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>